Methods for reinforcing existing lattice frame structures having hollow steel primary elements, particularly steel towers with tubular legs

ABSTRACT

A series of alternative related methods for reinforcing an existing lattice frame steel structure, having substantially vertical Hollow Primary Elements, offering the option to choose between improving only compressive load-bearing capacity of said hollow primary elements, or improving both their compressive and the tensile load-bearing capacities. 
     The compressive load-bearing capacity of said primary elements is increased by filling their internal cavities with non-shrink cement-based grout, in a slow and low-pressure procedure, hence ensuring the applicability of the present invention to practically any existing steel structure with hollow primary elements, regardless of their capacity to withstand internal pressure. 
     The tensile load-bearing capacity of all, or any part of said primary elements is increased by the insertion, prior to the grout-filling, of a longitudinal, continuous and substantially concentric tensile reinforcement member into each respective primary element, and anchoring it properly to its bottom. An axial pretension of predetermined magnitude is applied to the tensile reinforcement member prior to the grout-filling.

FIELD OF THE INVENTION

The present invention relates particularly to reinforcing existing steel lattice towers with tubular legs, supporting telecommunication or broadcast antennae, large signage or the like, and generally to reinforcing any type of lattice frame structure having hollow steel primary elements.

BACKGROUND OF THE INVENTION

A series of alternative related methods for reinforcing an existing lattice frame steel structure, having substantially vertical Hollow Primary Elements, offering the option to choose between improving only compressive load-bearing capacity of said hollow primary elements, or improving both their compressive and the tensile load-bearing capacities.

The compressive load-bearing capacity of said primary elements is increased by filling their internal cavities with non-shrink cement-based grout, in a slow and low-pressure procedure, hence ensuring the applicability of the present invention to practically any existing steel structure with hollow primary elements, regardless of their capacity to withstand internal pressure.

The tensile load-bearing capacity of all, or any part of said primary elements is increased by the insertion, prior to the grout-filling, of a longitudinal, continuous and substantially concentric tensile reinforcement member into each respective primary element, and anchoring it properly to its bottom. An axial pretension of predetermined magnitude is applied to the tensile reinforcement member prior to the grout-filling.

The numbers of tall tower structures constructed globally have been very significant and consistently increasing in the last two decades. The major industry sector leading said growth is the mobile telecom sector, but there are also some non-telecom applications that require tall towers of possible similar structural properties, such as large commercial signage or the like.

The vast majority of said towers are made of steel, and a significant portion of those steel towers have hollow leg members made of steel pipe. These tubular-legged towers are characterized, in most cases, by a continuous enclosed hollow cavity running vertically inside the leg, from top to bottom.

In recent years, as the number of mobile carriers in every country kept increasing, communities and authorities have been looking for ways to reduce the number of new tower structures within their jurisdictions, thereby calling for maximum use of existing towers and encouraging, or even forcing, co-location of many carriers' network infrastructure on those existing towers, thus contributing to a tower overloading problem, which is more frequently encountered.

Another phenomenon that contributes to the load capacity exhaustion of most existing tower structures is the introduction of new generation networks, which are planned to “co-exist” with the older generation networks for a significant period of time, thus significantly increasing the antenna and feeder cable sail-loads on most existing towers.

Accordingly, many tower-owner entities, such as mobile telecom carriers, face tower overload problems with an increasing number of their existing tower structures, and there is a felt need for, and an expected welcoming acceptance of, an economic solution for reinforcement of the existing tower structures, particularly if the reinforcing work on site would not necessitate the temporary removal of antennas, thus any interruption of services may be avoided.

PRIOR ART PUBLICATIONS

A large number of patents, patent applications and other prior art publications relate to reinforcing existing tubular towers, other tubular structures or the like.

The following publications are believed to be the most relevant for reference as prior art herein:

The patent publication No. US 2004123553 makes known a method of reinforcing a tower, which is provided by embedding a length the tower in a reinforcement column formed of reinforcement material. This method of reinforcing a tower comprising: forming a reinforcement column including: applying a fluid reinforcing material to embed a vertical length of the tower; and holding the fluid reinforcing material in place along the vertical length of the tower until it solidifies to form the reinforcement column having the length of tower embedded therein.

The patent publication No. EP1869270 makes known a method for reinforcing a metal tubular structure. The method involves introducing multiple linear carbon rods inside a metallic tubular structure to form a bundle whose geometric distribution is predetermined, where the rods have a resistance to traction greater than a predetermined value. A cement grout is injected inside an inner space of the structure such that the grout makes contact with an inner surface of the structure and covers the rods. An independent claim is also included for a metallic tubular structure comprising multiple linear carbon rods.

The patent publication No. JP9217419 makes known a reinforcing structure of steel frame member. The problem to be solved to accurately and easily reinforce steel frame members, by integrally forming divided members by a fastening members to constitute a reinforcing member and charging a filler between the reinforcing member and the steel frame member.

According the solution in the publication a circular steel pipe is cut in half to form divided members and the end of a preventive material against buckling is integrally joined to the divided member. Then the steel frame member is extended to both upward and downward directions and also diagonally to construct a leg of the steel tower or the like. The integrally formed divided member and the preventive material against buckling are positioned at the outer periphery of the steel frame member. And the divided member is oppositely arranged from the reverse side of the divided member positioned at the outer periphery of the steel frame member or the like and belt-form members are wound up at both ends of the divided members and the fastening parts are integrally connected by fastening them with bolts and nuts to form the reinforcing member. And further, mortar is charged in the reinforcing members and cured.

The patent publication No. JP2003321948 makes known a reinforcing and repairing method for existing steel tower made of hollow steel pipes. The problem to be solved to provide a reinforcing and repairing method for an existing steel tower made of hollow steel pipes, which can be performed easily at a low cost. According the solution in the publication a filler is placed under pressure at a low speed from a filler inlet provided at the lowest portion of an existing hollow steel pipe tower until the filler comes close to the lowest end portion of a preliminary mortar inlet.

The placement under pressure of the filler is interrupted, and a predetermined amount of preliminary mortar is supplied upward to the top position of the filler from the preliminary mortar inlet placed above the filler inlet. The filler is supplied again under pressure until the top reaches near an intermediate position of a top hopper provided in a hollow steel pipe located at the highest place of the main column member. Upon completion of the placement of the filler under pressure, surplus filler remaining in the top hopper is discarded when sedimentation is completed without hardening, the top hopper is removed and the top surface of the main column member is leveled.

According to the state of the art a solution was published for reinforcing tower legs by the KM Consulting Engineers from M. Bohlinger, on the website www.kmengr.com/tower.

Another solution was published on the website www.armortower.com of the Armor Tower Inc. from Ed Rosenbloom.

The aim of the present invention is to provide a series of related, efficient and cost-effective methods for reinforcing existing lattice frame structures having substantially vertical hollow steel primary elements, particularly reinforcing steel lattice towers with tubular legs.

The efficiency of such methods would be reflected, amongst other parameters, in their compatibility with the widest range of said existing structures, while their cost-effectiveness would be achieved, amongst other aspects, through minimizing the obstruction of the reinforcing execution work to the continuous performance of the equipment or systems mounted on said structure, such as telecom systems for example.

During the development of the solutions presented by the present invention it was realized, that filling the cavities of the substantially vertical hollow steel primary elements of the existing structure with non-shrink cement grout provides an effective increase of the compressive load-bearing capacity of said primary elements, however all methods of prior art for executing said grout filling are based on injection of the grout from the bottom upwards, in techniques that require application of high pressures inside said hollow primary elements. In certain existing structures, especially where said hollow primary elements are made of longitudinally seamed pipes of relatively large diameter and small wall-thickness, applying such high pressures is not desired or not allowed, due to the limited capacity of said existing primary elements to sustain such internal pressures. The innovation of the present invention is the facility to execute said grout-filling while drastically reducing said internal pressures to any low value prescribed by the project designer, by eliminating the need to keep the grout in constant flow inside said cavity of a respective hollow primary element being filled. This, in turn, is achieved by utilizing an inserted hosepipe, which is lowered into substantially the bottom of said cavity of said respective hollow primary element through an opening at its top, and injecting the grout down said inserted hosepipe in as slow pace as desired, while retracting said hosepipe upwards in a pace that matches the rise of the grout level inside said primary element being filled.

It was further realized that, in certain types of said existing structures, in order to achieve a significant overall improvement in the capacity of said structure to withstand lateral loads, such as wind loads, not only increasing the compressive load-bearing capacity of its hollow primary elements is required, but also increasing the tensile load-bearing capacity of part, or all of them. The innovation of the present invention is the introduction of a series of related methods for increasing said tensile load-bearing capacity of any of said hollow primary elements, in combination with its grout filling by any method whatsoever, which is achieved by the insertion prior to the grout-filling, of a longitudinal, continuous and substantially concentric tensile reinforcement member, anchoring it properly to the bottom of said hollow primary element, then applying to it an axial pretension of a predetermined magnitude through a top tensioning apparatus, which also fixes its top end during the grout-filling process and at least until the grout is cured and hardened. The tensile reinforcement member may be made of a steel rod, preferably in segments coupled to each other, or of a steel strand or wire rope, or of a combination of segments of rods and strand (or wire rope).

SUMMARY OF THE INVENTION

The present invention provides a series of alternative related methods for an efficient and cost-effective reinforcing of an existing steel lattice tower with tubular legs, or of any other lattice frame structure having hollow steel primary elements.

One important advantage of the methods provided by the present invention is, that they offer the designer the option to choose between improving only the compressive load-bearing capacity of the existing structure's primary elements, or improving both the compressive and the tensile load-bearing capacities of said primary elements. Obviously, the improvement of both the compressive and the tensile load-bearing capacities involves a higher level investment, which might be inevitable with those structures where the existing primary elements might be overstressed by expected tensional loads. In other structures, the primary elements might come under overstressing only by the expected compressive loads, and the problem may be solved at a lower level of investment. Hence, an optimized reinforcing solution may be tailored by the structural designer, considering the specific characteristics of the specific structure.

Another important advantage of the methods provided by the present invention, in the context of reinforcing Telecom Network towers, is that the reinforcing work may take place without necessitating the temporary removal of antennas from the tower, hence no interruption of services is required.

According to one group of applications of the present invention, the compressive load-bearing capacity of each of the structure's hollow primary elements (the legs in the case of towers) is increased by filling its internal cavity with non-shrink cement-based grout, in an innovative slow and low-pressure procedure. In this procedure, a Grout-Feeding Subsystem, arranged according to one of many feasible alternatives, supplies fresh grout mixture at the top of the structure being reinforced, with a relatively low output pressure, and desirably relatively slow flow capacity as well, and the grout is then placed in its final position within the hollow primary element using a hosepipe inserted and lowered down to the bottom of said primary element, and said hosepipe is in turn retracted outwards from the primary element in a pace matching the raise of grout level. The slow pace of the grout level raising ensures, amongst other things, a limited hydrostatic pressure build-up, even at the lower parts of the filled-up element, as the grout may be allowed to cure and harden during the process itself, such that the height of the fresh mixture within the element is kept within a pre-determined value.

When several similar elements of the structure need to be filled-up with grout, such as the 3 or 4 legs of a telecom tower, the filling method facilitates the almost simultaneous filling of all these similar elements, hence the overall filling task may be completed within a reasonable period of time, despite the need to limit the pace of grout level rising.

The use of grout filling to reinforce hollow steel elements is a practice known in the art for several years, but the procedure practiced to date to fill tall structures, such as tower legs, is based on fast and high pressure filling of the cavity from the bottom upwards. A precondition for the applicability of the procedure practiced to date is that the primary hollow structure elements, which are to be filled-up, have the capacity to sustain safely the extremely high pressure levels that are applied in the process. This precondition might not be met in the case of some existing structures, as either the parameters of their original design or the age of the structure might hamper this capacity. Furthermore, the procedure practiced to date is considered to be fairly complicated and risky, it necessitates the use of costly specialized equipment and the application of equipment break-up plan (which means additional back-up equipment), and therefore it must be carried out exclusively by a contractor having the necessary experience and equipment.

The innovative slow and low-pressure method, according to said application of the present invention, overcomes the abovementioned limitations of the procedure practiced to date. Furthermore, it does not necessitate, in most cases, the modification of the existing structure for the purpose of the grout filling (such as drilling and welding of grout-inlet apparatus onto the bottom of the hollow element), thus such local damage to the corrosion-protection system of the existing structure may also be avoided.

According to an improved version of said application of the present invention, the grout-filling process may be monitored and verified to be free of unaccountable obstructions, and the process may be electronically-documented, through the use of a specialized remote camera system. The camera itself is appropriately small and durable, with integrated flashlight, in order to be lowered into the filled-up element alongside the hosepipe, and record the filling process from a close range while being retracted upwards at a pace matching the pace of the grout filling.

According to an alternative group of applications of the present invention, in addition to increasing the compressive load-bearing capacity of the structure's hollow primary elements (through any kind of grout-filling method or procedure), the tensile load-bearing capacity of all, or any part of the same primary elements is also increased simultaneously. The increase in tensile load-bearing capacity is achieved by the insertion, prior to the grout-filling, of a longitudinal, continuous and substantially concentric tensile reinforcement member, and anchoring it properly to the bottom of the primary structure element being reinforced (in the case of a tower: at the bottom of the tower leg). Then an axial pretension of a predetermined magnitude is applied to the tensile reinforcement member, and the top end temporarily fixed so as to allow the commencement of the grout-filling.

The tensile reinforcement member may be made of a steel rod or a steel strand. When the axis of the primary structure element being reinforced (in the case of a tower: the axis of the tower leg) is arranged along a straight line throughout its length, the utilization of a stiff continuous steel rod may prove to be the most cost-effective choice. However when the said axis is not straight (as is the typical case with most self-supporting telecom towers, where said axis has a break-point between a vertical-legged top portion and an inclined-legged structure underneath it) the insertion of stiff rod, with a required cross-section, from the top down might, in certain cases, prove impossible. In those cases the tensile reinforcement member should preferably be made of a steel strand.

In some extreme applications, the use of a rod or a strand having a higher tensile modulus than that of steel might be inevitable, in those extreme cases the tensile reinforcement member may be made of a superior material (carbon rods or the like).

In an optimized design, a substantially constant proportion should be maintained between the cross-sectional area of the original hollow section and that of the tensile reinforcement member. In the case of a tower structure, for example, that means that as the original cross-sectional area of the leg is normally decreasing in a stepped manner, from the bottom upwards, so should preferably also the cross-sectional area of the tensile reinforcement member step down gradually. Another reason that may necessitate this gradual variation in the cross section of the tensile reinforcement member, is the space constraints within the tubular leg: Throughout the length of the leg, sufficiently large clear distance between the central tensile reinforcement member and the inner wall of the steel pipe must be maintained, to allow passage for the inserted hosepipe transporting the grout. In most cases, this constraint sets a stringent limit on the “allowable” diameter of the tensile reinforcement member in the upper portion. At the same time, the diameter of the tensile reinforcement member at the bottom section must be large enough, so as to ensure the said reasonable strength proportion with the leg's original steel pipe at that bottom end. Hence, the only way to harmonize these two conflicting constraints is to produce a tensile reinforcement member with a varying cross-sectional area, largest at the bottom end and decreasing gradually towards the top.

The invention is a method for reinforcing an existing lattice frame steel structure or tower (10) having substantially vertical Hollow Primary Elements (11), by filling the continuous longitudinal cavities of said Hollow Primary Elements with a non-shrink cement-based Grout, in a slow and low-pressure procedure, and in a sequential order, wherein said method comprises:

-   -   a. Gaining access to said continuous longitudinal cavity of said         respective Primary Element (11) through an Inlet Opening (16)         located at its top, either by removing a cap plate or another         bolted element sealing said existing Inlet Opening (16), or         otherwise cutting or drilling such Inlet Opening through the top         of said Primary Element (11) to be reinforced;     -   b. Lowering an Inserted Hosepipe (22) into each respective said         Primary Element (11) to be reinforced, through said respective         Inlet Opening (16), each of said Inserted Hosepipe (22) being         long enough to reach substantially the bottom of said respective         Hollow Primary Element (11), such that a relatively short part         of said inserted Hosepipe (22) projects outward from the top of         respective Primary Element (11);     -   c. Sealing (in as much as necessary) any openings at the bottom         of said Hollow Primary Elements (11) or at any higher point,         through which the grout might leak out, except for the Inlet         Opening (16);     -   d. Preparing a Grout-Feeding Subsystem comprising:         -   (i) A Bottom Grout Pump (24), which is a high-pressure             grout-pump (typically of a type readily available in the             market), located at ground level, near a Grout Mixing Device             (25) (also typically of a type readily available in the             market). Grout Pump (24) and Grout Mixing Device (25) may be             combined in the same machine; and         -   (ii) A substantially vertical Exterior Grout Pipe (27),             which is typically a flexible, high pressure hose available             in the market as an accessory of Bottom Grout Pump (24), but             may also be made of a tailored, rigid metallic pipe-line,             laid between Bottom Grout Pump (24) and substantially the             top of the Structure (10) being reinforced, its bottom end             being connected to Outlet Stub (26) of Pump (24), and its             top end being connected to one of the top intake-ends of             said Inserted Hosepipes (22), through a Step-Down             Hose-Coupler (28), fitted to engage the larger cross-section             of Grout Pipe (27) on one side, and the smaller             cross-section of Hosepipe (22) on the other;     -   e. “Feeding” said Bottom Grout Pump (24) with appropriate volume         of fresh Grout mix, prepared using said Grout Mixing Device (25)         in timed batched, as necessary to match the pace of the Grout         filling process;     -   f. Pumping the Grout through said Exterior Grout Pipe (27) up to         the top of Structure (10) and further into said respective         Hollow. Primary Element (11), through said Inserted Hosepipe         (22), at such a slow pace (including possible planned pauses)         that ensures that the height of the fresh Grout (i.e. the not         yet hardened grout) within the Hollow Primary Element (11) does         not exceed a predetermined value. During this process of grout         filling of a single Hollow Primary Element (11), Hosepipe (22)         is being retracted gradually upwards through said Inlet Opening         (16), at a pace that matches the raise of the grout level within         the respective Primary Element (11). Depending on the         characteristics of Hosepipe (22), its retracted and exposed         portion may be collected in hoops substantially at the top of         Structure (10), or alternatively the exposed portion being cut         off, from time to time, and the top end of the remaining         Hosepipe (22) reconnected to said Grout-Feeding Subsystem;     -   g. Following the complete filling of the first Hollow Primary         Element (11) with grout, up to the prescribed final level,         repeating the procedure described in points e & f above for each         of the other Hollow Primary Elements (11), in a sequential         order.

In a preferred application of the method according to the invention the handling of said Inserted Hosepipe (22) is assisted by auxiliary means comprising:

-   -   a. Fixing a Hand Winch (100), equipped with compatible thin         Winch Rope (101) with length equal at least to substantially the         initial length of Inserted Hosepipe (22), above said Inlet         Opening (16) of respective Primary Element (11), with a         relatively small vertical gap there between;     -   b. Attaching said Winch Rope (101) to respective Hosepipe (22),         before or during its insertion into Primary Element (11), by         means of an End Fastening Device (102) located near said         Hosepipe's Outlet End (105), and a plurality of Intermediate         Fastenings (103) located in certain appropriate intervals         throughout the inserted length of Hosepipe (22) and Winch Rope         (101). The selection of specific appropriate materials and shape         for Fastening Devices (102) and (103) is significantly governed         by the dimensional constraints inside the cavity of said Primary         Element (11), and also by the materials of Hosepipe (22) and         Winch Rope (101);     -   c. Retraction of Hosepipe (22) is facilitated by turning Hand         Winch (100), while said small vertical gap between Inlet Opening         (16) and Hand Winch (100) allows dismantling each Intermediate         Fastening (103) as soon as it is exposed, thus allowing handling         of the exposed portion of said Hosepipe (22) independently from         the auxiliary means described herein.

In another preferred application of the method according to the invention said Grout-Feeding Subsystem further comprises:

-   -   (i) A grout Buffer Tank (20) of appropriate size, placed near         the top of said Existing Structure (10) being reinforced, and         having a bottom outlet nozzle; and     -   (ii) A Top Grout Pump (21) (electrical or manual), placed         slightly lower than said Buffer Tank (20) and connected to said         Tank's outlet nozzle, directly or through a relatively short         pipe there between;     -   and wherein said top end of Exterior Grout Pipe (27), is placed         right over said Buffer Tank (20) so as to feed it with fresh         grout, such that Bottom Grout Pump (24) and Exterior Grout Pipe         (27) are used only to “feed” Buffer Tank (20) with fresh grout         at the required capacity, while Top Grout Pump (21) ensures         required drive for the grout to flow along the entire length of         Inserted Hosepipes (22), one of which is being connected         directly to its outlet.

In a further preferred application of the method according to the invention said Grout-Feeding Subsystem does NOT include the Bottom Grout Pump (24) and the Exterior Grout Pipe (27), and instead the “feeding” of Buffer Tank (20) with fresh grout, which is being prepared utilizing said Grout Mixing Device (25) at ground level, is achieved by lifting the ready grout mix into said Buffer Tank (20) in buckets, utilizing any one of many practices exercised conventionally in the construction industry.

In a further preferred application of the method according to the invention said Grout Mixing Device (25) is located on an auxiliary platform, substantially at the top of said Existing Structure (10) being reinforced, such that it directly “feeds” Buffer Tank (20) with fresh grout, and wherein the dry grout bags may be positioned beforehand on said auxiliary platform or sufficiently close to it, so as to facilitate the mixing operation at the required pace.

In a further preferred application of the method according to the invention said filling of the cavities of said Hollow Primary Elements (11) with said Grout is done in an almost simultaneous manner (instead of sequentially), the method employing a plurality of said Inserted Hosepipes (22), such that each of said Hollow Primary Elements (11) has one of said Inserted Hosepipes (22) lowered there into, through its respective Inlet Opening (16), and the top intake end of each of said Inserted Hosepipes (22) is connected to said Grout-Feeding Subsystem only for a relatively short duration at a time, facilitating only partial filling of the respective Hollow Primary Element (11), following which the top intake end of another Inserted Hosepipe (22) is connected to said Grout-Feeding Subsystem only for a short duration, so as to facilitate similar partial filling of the other respective Hollow Primary Element (11), and this procedure is repeated with all said Inserted Hosepipes in a sequential and cyclic manner, maintaining the Grout level differences between the various Hollow Primary Elements within a predetermined value, until the grout level in all said Hollow Primary Elements (11) has reached the prescribed final levels.

In a further preferred application of the method according to the invention a Multi-Valve Distribution Block (23) is connected to the outlet of said Grout-Feeding Subsystem, the number of valves in said Distribution Block (23) being equal (or exceeding) the number of said Hollow Primary Elements (11) to be filled with Grout substantially simultaneously, and each of said top intake ends of Inserted Hosepipes (22) is connected to one respective valve in said Distribution Block (23), facilitating either simultaneous flow of the grout into all respective Hollow Primary Elements (11), or only into one of them at any given short duration, in a cyclic switching procedure, so as to achieve the same effect of almost simultaneous Grout filling at a higher comfort and speed.

In a further preferred application of the method according to the invention said filling, of said cavities, with said Gout, is monitored through a specialized Remote Portable Camera System, so as to verify that it is free of any unforeseen obstructions, the Camera (or plurality of cameras, respectively) of said System being appropriately small and durable, having an integrated flashlight; said Camera is lowered into the respective Hollow Primary Element (11) through said Inlet Opening (16) alongside with said respective Inserted Hosepipe (22), so as to provide a real-time, close-range electronic image of the filling process, and is also retracted upwards together with the respective Inserted Hosepipe (22), so as follow the rise of the grout level inside respective Primary Element (11) being filled.

In a further preferred application of the method according to the invention said Remote Portable Camera System further facilitates recording of the video signals obtained through said Camera (or plurality of cameras), thus the entire said Grout-filling process may be electronically-documented.

The invention further is a method for increasing the tensile load bearing capacity of all, or part of the substantially vertical Hollow Primary Elements (11) of an existing lattice frame steel structure (10), to be used in conjunction with grout-filling of said Hollow Primary Elements (11) performed by any method whatsoever, wherein said method comprises:

-   -   a. Preparing a respective required quantity of a longitudinal,         continuous Tensile Reinforcement Member (30), made of steel and         having a Bottom End Fitting (51) designed to engage a respective         Bottom Anchoring Apparatus (50), said Bottom End Fitting (51)         being sufficiently small to pass through the respective top         Inlet Opening (16) and through the narrowest part of the         internal cavity of respective Hollow Primary Element (11);     -   b. Preparing a respective required quantity of Top Tensioning         Apparatus (60), each tailored to fit the respective typical         existing top flange (15) or another existing connecting         apparatus near top Inlet Opening (16) of the respective Hollow         Primary Element (11), and constructed in a way that would not         obstruct the insertion of the Tensile Reinforcement Member (30)         into said respective Hollow Primary Element (11), and if         applicable: would also facilitate the handling (namely insertion         and retracting) of an Inserted Hosepipe (22);     -   c. Inserting each of said Tensile Reinforcement Member (30) into         the respective Hollow Primary Element (11), until its respective         Bottom End Fitting (51) reaches the bottom of the respective         Primary Element (11), and its top end is suspended from said Top         Tensioning Apparatus (60);     -   d. Installing and fixing the complete Bottom Anchoring Apparatus         (50) between the bottom part of the respective Hollow Primary         Element (11) and the Bottom End Fitting (51) of the respective         Tensile Reinforcement Member (30);     -   e. Applying an axial pretension of predetermined magnitude to         said respective Tensile Reinforcement Member (30), through said         Top Tensioning Apparatus (60);     -   f. Filling the entire internal cavity of said respective Hollow         Primary Element (11), or any part thereof as prescribed by the         structural designer, with cement-based non-shrink grout.

In a preferred application of the method according to the invention the tensioning means in said Top Tensioning Apparatus (60) comprises a conventional turnbuckle (61).

In another preferred application of the method according to the invention the tensioning means in said Top Tensioning Apparatus (60) comprises a threaded rod (62) passing, substantially vertically, through a rigid top cover plate of Top Tensioning Apparatus (60), whereby the tensioning is applied by tightening of a top Tensioning Nut (63).

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) is made of a plurality of long steel Rods (31) all of which having substantially equal cross-section, each of said Rods (31) having threaded end portions (34, 35) at both its ends, a plurality of Threaded Couplers (81) equipped with matching internal threads, and a Bottom End Fitting (51) equipped with matching internal thread as well, and wherein the process of installing said Tensile Reinforcement Member (30) starts with threading said Bottom End Fitting (51) onto the bottom-most of said steel Rods (31), then all said steel Rods (31) are sequentially coupled to each other, through said Threaded Couplers (81), during the process of inserting the Tensile Reinforcement Member (30) into the respective Hollow Primary Element (11).

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) is made of a plurality of long steel Rods (31 through 33) made in several different cross-sectional dimensions, each of said Rods (31 through 33) having threaded end portions (34 through 39) at both its ends, a plurality of Threaded Couplers of several matching sizes (81, 82) equipped with matching internal threads, and a Bottom End Fitting (51) equipped with internal thread matching the bottom thread (39) of the bottom-most Rod. The number of Rods (31 through 33) may be larger than the number of different cross-sectional dimensions, such that a plurality of said rods may be of similar cross-section. Rods (31 through 33) make up a complete Tensile Reinforcement Member (30) such that its bottom portion is made of the largest cross-section Rods (33), and the cross-sections are stepping down in certain designed step-down coupling locations, wherein the top-end thread (36, 38 respectively) of the lower joining Rod (32, 33 respectively) is made smaller than the typical size thread (37, 39 respectively) of the respective Rod, so as to match the smaller size thread of the joining Coupler (81, 82 respectively), which in turn matches the thread (35, 37 respectively) of the upper joining Rod (31, 32 respectively), and wherein the process of installing said Tensile Reinforcement Member (30) starts with threading said Bottom End Fitting (51) onto the bottom-most of said steel Rods (33), then all said steel Rods (33 through 31) are sequentially coupled to each other, through said Threaded Couplers (82, 81), during the process of inserting the Tensile Reinforcement Member (30) into the respective Hollow Primary Element (11).

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) is made of a single continuous Steel Wire Strand or Wire Rope, of uniform cross-section throughout its length, and is equipped with a Bottom End Fitting (51) engineered and mounted onto its bottom end according to any common practice known in the wire rope industry.

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) is made of several segments of a Steel Wire Strand or Wire Rope (41 through 43), each made with a different cross-section, the bottom, thickest segment (43) is equipped with a Bottom End Fitting (51) engineered and mounted onto its bottom end according to any common practice known in the wire rope industry, and the other segments (42, 41) being coupled with each other and with the thickest segment (43) in a cross-sectional stepping down sequence, with splicing means (71, 72) based on any common practice known in the wire rope industry, so as to make up a complete Tensile Reinforcement Member (30).

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) is made of a single continuous Steel Wire Strand, the cross-section of which consists several layers of wires arranged in concentric circles, said Tensile Reinforcement Member (30) being divided into a plurality of segments (141 through 144), the cross-sectional dimensions of said segments stepping-down respectively, said stepping-down of the Wire Strand's cross-sectional dimensions is obtained by peeling off a layer of the wires at each stepping down point, such that the cross-section of the bottom-most segment is equal to the Wire Strand's original cross-section, and the upper-most segment has the largest number of wire layers peeled off, and wherein said Tensile Reinforcement Member (30) further including a Bottom End Fitting (51) engineered and mounted onto the bottom end of its bottom segment (144) according to any common practice known in the wire strand industry.

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) further includes protecting metal sleeves (149) of appropriate dimensions, fitted and crimped onto the Wire Strand's cross-sectional step-down points, so as to prevent undesired local deterioration of the Strand's structure at these locations during winding and handling.

In a further preferred application of the method according to the invention the longitudinal axes of all or part of the Hollow Primary Elements (11) of the existing structure have a breaking (turning) point at a certain intermediate location along their height, and said method includes the utilization of sufficient number of Restrainer (90), each being mounted onto a respective Hollow Primary Element (11) at a location close to said axial breaking point, after cutting or drilling an appropriate small opening through the wall of the respective Hollow Primary Element (11) at said location, each said Restrainer (90) being shaped and sized so as to maintain the axis of the Tensile Reinforcement Member (30) substantially concentric with that of the respective Hollow Primary Element (11).

In a further preferred application of the method according to the invention said Restrainer (90) comprises an Insert (150) inserted into the respective Hollow Primary Element (11) through a hole (160) drilled in its wall, Insert (150) being designed to stay permanently within the reinforced structure, and further comprises temporary supporting and fastening means, designed to firmly hold Insert (150) in place during the grout-filling process, all of said temporary supporting and fastening means being mounted on the exterior of the respective Hollow Primary Element (11) thus being removable and reusable; the length of insert 150 determined so as to restrain Tensile Reinforcement Member (41 in FIGS. 20, 21) in the designed, substantially concentric location, its free end shaped with an alcove matching the cross-section of Tensile Reinforcement Member (41), and its rear end equipped with a threaded bore (158) so as to facilitate connection to said temporary supporting and fastening means by a removable bolt (155).

In a further preferred application of the method according to the invention said temporary supporting and fastening means comprise a clamping device fitted to the cross-section of Hollow Primary Element (11), made commonly of 2 parts (151, 152), bolted to each other with bolts (153) and nuts (154), one respective part of the clamp (151) having a drilled hole with a location and size matching those of said threaded bore (158) in Insert (150), and a bolt (155) which secures Insert (150) onto said clamp (151).

In a further preferred application of the method according to the invention the bottom end of said existing Hollow Primary Element (11) is fitted with a flat base flange (13) leaving an opening at its bottom, wherein a certain a deliberate Vertical Gap exists between the bottom surface of Flange (13) and the concrete foundation, wherein said Bottom Anchoring Apparatus (50) is designed as a simple, monolithic Beam (180) with a height not exceeding said Vertical Gap and a length sufficiently larger than the bottom opening in Flange (13), and wherein said Bottom End Fitting (51) is shaped uniquely as a Fitting (181) equipped with a bore substantially transverse to its longitudinal axis, shaped and dimensioned to facilitate the passage of Beam (180) there through, with good dimensional fit there between.

In a further preferred application of the method according to the invention the bottom end of said existing Hollow Primary Element (11) is fitted with a flat base flange (13) leaving an opening at its bottom, wherein a certain a deliberate Vertical Gap exists between the bottom surface of Flange (13) and the concrete foundation, wherein said Bottom End Fitting (51) comprises a top part (110) mounted onto the bottom end of the respective Tensile Reinforcement Member (44 in FIGS. 10, 11 & 12), and heaving a substantially vertical threaded bore at its bottom, and a bottom part (111) which is a matching bolt, possibly having a specially shaped head, and wherein said Bottom Anchoring Apparatus (50) comprises a longitudinally & vertically split beam consisting two parts (112, 113) which may be identical or differ in shape, each containing a shaped groove, such that when the beam consisting the two parts (112, 113) is assembled, it snugly houses the head-part of bolt (111); the height of each beam part (112, 113) not exceeding said Vertical Gap, its length being sufficiently larger than the bottom opening in Flange (13), and the two beam parts (112, 113) being secured to each other after assembly with bolts (114) and nuts (115).

In a further preferred application of the method according to the invention the bottom end of said existing Hollow Primary Element (11) is fitted with a flat base flange (13) leaving a sufficiently large opening at its bottom, wherein a certain a deliberate Vertical Gap exists between the bottom surface of Flange (13) and the concrete foundation, wherein said Bottom End Fitting (51) is shaped as a Fitting (120) having two parallel flat faces on both its sides and a through-passing smooth bore with an axis substantially perpendicular to said two parallel flat faces and to the axis of the Tensile Reinforcement Member (44 in FIGS. 13, 14 & 15), and wherein said Bottom Anchoring Apparatus (50) comprises two substantially identical beams (121) clamping End Fitting (120) there between, each of said beams (121) being made of a steel plate positioned vertically, having a transverse through-passing smooth bore matching in size said bore of said End Fitting (120), and shaped such that its central portion may be somewhat higher than said Vertical Gap, said Bottom Anchoring Apparatus further comprising a relatively thick Connecting Pin (122) dimensioned to sustain the expected shear loads and long enough to secure both beams (121) onto End Fitting (120), machined smooth along its central portion and having smaller diameter threads on both ends, so as to facilitate tightening with one or two nuts (123) and large washers (124) that are larger than said smooth bores.

In a further preferred application of the method according to the invention said relatively thick Connecting Pin (122) does not have said smaller diameter threads at its ends, and said clamping of said End Fitting (120) between said two plate beams (121) is secured by separate, at least two long bolts, passing transversely through both said plate beams (121) without contacting said End Fitting (120), such that tightening said separate long bolts ensures that both plate beams (121) tightly abut said two parallel flat faces on both sides of End Fitting (120), while said Connecting Pin (122) is positioned in said through-passing smooth bores of said End Fitting (120) and of both said plate beams (121).

In a further preferred application of the method according to the invention the bottom end of said existing Hollow Primary Element (11) does not include any opening (or wherein a designer's choice is not to utilize such existing opening) wherein said Bottom Anchoring Apparatus (50) is designed as a simple Beam (132), passing transversely through said existing Hollow Primary Element (11), after cutting on site two openings in its walls in appropriate sizes and locations, and optional reinforcing of the cut openings by welded plates (133, 134), in one or more layers, may be utilized such that, while the field cuttings of said Primary Element (11) might be rough and the resulting openings too large, said reinforcing plated (133, 134) may have shop-machined openings, matching the cross-sectional shape of Beam (132), thus ensuring a tight fit there between, and wherein said Bottom End Fitting (51) of the Tensile Reinforcement Member (44 in FIGS. 16, 17 & 18) is shaped uniquely as a Fitting 131 equipped with a transverse bore shaped and dimensioned to facilitate the passage of beam (132) there through, with a good geometric fit there between.

In a further preferred application of the method according to the invention said Tensile Reinforcement Member (30) is made of a combination of steel rods and wire strands or wire ropes, in various segments, spliced together so as to make up a complete Tensile Reinforcement Member (30) in the required length.

In a further preferred application of the method according to the invention the tensile load bearing capacity of the existing anchoring system, at the bottom of any Primary Element (11), is also reinforced by any procedure commonly practiced in the art, such as welding appropriate, substantially horizontal steel plates (204), having a required number of holes for additional anchoring bolts (200), onto the bottom end of said Primary Element (11), and drilling into the concrete foundation and installing with the utilization of appropriate epoxy resin (201) or the like, a required number of said additional anchor bolts (200), tightening the nuts (203) of said additional anchor bolts (200) after said resin (201) has cured, and possibly encasing the entire reinforced base in a protective mass of non-shrink concrete (202).

In a further preferred application of the method according to the invention the entire reinforcement of the structure further includes improving the load bearing capacity of secondary elements, namely certain lattice brace members of the structure, by any procedure commonly practiced in the art, such as the replacement of said certain lattice brace members of a bolted Existing Structure (10) with new brace members having larger cross-sectional area, and/or other improved properties.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention, as well as some preferred applications thereof, may be best understood and appreciated from the following detailed description made in conjunction with the drawings in which:

FIG. 1 is a schematic chart illustrating one application of a method for the grout-filling of the Hollow, substantially vertical Primary Elements of an existing, relatively tall steel structure, with a controlled build-up of the hydrostatic pressure inside said primary elements;

FIG. 2 is a schematic chart illustrating another application of a method for such slow and low-pressure grout-filling of said Hollow Primary Elements;

FIG. 3 is a schematic chart illustrating one embodiment of arranging the Tensile Reinforcement Member inside a simple existing Hollow Primary Element having a straight axis;

FIG. 4 is a schematic chart illustrating another embodiment of arranging the Tensile Reinforcement Member inside an existing Hollow Primary Element having a non-straight axis;

FIG. 5 is a schematic chart illustrating one embodiment of constructing the Tensile Reinforcement Member from a plurality of Steel Rods, made with stepping cross-sectional dimensions and coupled together using threaded couplers of various respective thread dimensions;

FIG. 6 is a schematic chart illustrating one embodiment of constructing the Tensile Reinforcement Member from a continuous Steel Wire Strand, consisting of a plurality of segments with stepping-down cross-sectional dimensions, where said stepping-down is obtained by peeling off an additional layer of the strand's wires at each stepping down point;

FIGS. 7, 8 & 9 illustrate one embodiment of anchoring the bottom end of the Tensile Reinforcement Member to the bottom of the existing Hollow Primary Element, where said bottom end of said Primary Element is formed with a Base Flange, raised above the concrete foundation with a certain gap (meant to facilitate post-erection leveling of the structure);

FIGS. 10, 11 & 12 illustrate another embodiment of said anchoring of said Tensile Reinforcement Member's bottom end, assuming similar features of the base of the existing structure;

FIGS. 13, 14 & 15 illustrate yet another embodiment of said anchoring of said Tensile Reinforcement Member's bottom end, assuming similar features of the base of the existing structure;

FIGS. 16, 17 & 18 illustrate one embodiment of said anchoring of said Tensile Reinforcement Member's bottom end, where there is no existing access from the bottom to the interior cavity of the existing Hollow Primary Element, or where the designer prefers not to utilize such existing access for whatever reason;

FIG. 19 illustrates schematically one embodiment of increasing the tensile load bearing capacity of the existing structure's anchoring system, utilizing a procedure commonly practiced in the art;

FIGS. 20 & 21 illustrate one embodiment of a Restrainer, shaped and sized so as to maintain the axis of the Tensile Reinforcement Member substantially concentric with that of the respective existing Hollow Primary Element, where the longitudinal axis said Primary Element has a breaking (turning) point at a certain intermediate location;

FIG. 22 illustrates schematically one embodiment of the auxiliary means for the handling and gradual retracting of the Hosepipe inserted into the Primary Element being reinforced, for the purpose of grout filling.

DETAILED DESCRIPTION OF THE INVENTION

The objective of the present invention is to provide a series of related methods for the efficient and cost-effective reinforcing of an existing lattice frame steel structure having substantially vertical hollow steel primary elements, such as steel lattice tower with tubular legs or the like.

The invention provides two main innovative method groups, which may be combined with each other or applied individually on separate cases:

-   1. A group of methods for improving the compressive load-bearing     capacity of the existing structure's primary elements, by filling     them with a cement-based non-shrink Grout in a slow and low-pressure     procedure, which makes this method applicable with practically any     existing steel structure having hollow primary elements, regardless     of their capacity to withstand internal pressure; -   2. A group of methods for improving the tensile load-bearing     capacity of all, or any part of said primary elements, which is to     be applied in conjunction with grout-filling of said primary     elements, regardless if said grout-filling is performed according to     the principles of the present invention or based on other techniques     known in the art. The said improvement in tensile load-bearing     capacity is obtained by the insertion, prior to the grout-filling,     of a longitudinal, continuous and substantially concentric tensile     reinforcement member into each respective primary element, and     anchoring it properly to its bottom. An axial pretension of     predetermined magnitude is applied to the tensile reinforcement     member prior to the grout-filling.

Hence, an important advantage of the methods provided by the present invention is that they facilitate the “tailoring” of an optimized reinforcing solution by the structural designer, considering the specific characteristics of the specific structure.

FIG. 1 illustrates schematically one application of a method for the slow and low-pressure procedure of grout-filling. A typical existing 3-legged steel lattice tower 10, having tubular legs, of the type used commonly in wireless telecom networks, is illustrated in FIG. 1, where the Hollow Primary Elements 11 (also known as Tower Legs) are made of individual pipe sections coupled to each other through welded bolting flanges 12, these flanges configured typically such, that they do not obstruct the interior cavity, which runs continuously within Tower Leg 11 from top to bottom. The Base Flanges 13 of the tower are typically anchored down to a concrete foundation by Anchor Bolts 14. The top end of each Hollow Primary Element (Tower Leg) 11 is typically equipped with a top flange 15 which typically leaves the top end of Hollow Primary Element 11 open, or covered with a removable cap-plate. Said open end is used as Inlet Opening 16, through which the grout-filling process takes place. In those rare cases where the Hollow Primary Element 11 does not contain such a ready Inlet Opening 16, it must be drilled or cut by conventional means, so as to form Inlet Opening 16.

A basic principle of the slow and low-pressure grout-filling methods disclosed in the present invention is the “lack of flow”, or rather “motionless” of the grout inside Hollow Primary Elements 11, once poured there into. Hence, as opposed to the “pumping from the bottom” techniques known in the art, according to which the grout must be kept in constant flow within Primary Elements 11 throughout the filling process, and therefore the entire filling process must be very fast and involve very high pumping pressures, as well as high grout-mixing capacities, in the grout-filling methods based on the present invention the mass of grout is being built-up within said Primary Elements 11 from the bottom upwards, and every poured particle of grout remains stationary and may be allowed to cure and harden once poured into respective Primary Element 11, regardless of the duration of the entire filling process. Owing to this property, the internal hydrostatic pressure levels sustained by the filled. Primary Element 11 may be kept as low as desired or planned. Furthermore, these methods may be applied using relatively simple equipment, and the impact of equipment failure is far less critical than that in the case of the “pumping from the bottom” techniques known in the art.

The abovementioned “motionless grout” phenomenon is facilitated by the “pouring through the top” principle, which is a basic conceptual innovation of the present invention, and is practically achieved through the utilization of Inserted Hosepipe 22, the bottom outlet-end of which is lowered, in the beginning of the filling process, down into substantially the bottom of Hollow Primary Element 11. During the grout-filling process, Inserted Hosepipe 22 is gradually retracted upwards in a pace corresponding to the raise of the grout level inside said Primary Element 11. The utilization of Inserted Hosepipe 22, as described above, is the professionally adequate method for implementing the mentioned “pouring through the top” principle, as the alternative option of direct pouring of the grout through top Inlet Opening 16 is professionally inadequate, for the following reasons: (a) uncontrolled falling of the grout from a great height, inside filled Primary Element 11, might result in severe segregation, namely non-homogeneity of the grout mixture, and (b) build-up of the freely “spilled” grout on the interior walls of filled Primary Element 11, during the filling process, might result in uncontrolled caulking of the inner longitudinal cavity of Primary Element 11, and consequently the creation of undesired permanent air cavities instead of a continuous grout mass.

Due to typical space constraints inside the respective filled Primary Element 11, the feasibly allowable cross-sectional dimensions of Inserted Hosepipe 22 are very small, a constraint that increases the frictional resistance to free flow of the grout through said Hosepipe 22. For this reason the filling system and the arrangement of its components must ensure, that the fresh grout is fed into the top intake-end of Inserted Hosepipe 22 with sufficient pressure, so as to facilitate the desired flow of grout despite said increased resistance. In most practical applications of the present invention, said sufficient pressure should be a relatively low pressure, as the capacity of Inserted Hosepipe 22, given the mentioned geometric constraints, to withstand internal pressure is limited. An appropriate cement-based grout product must be selected and used, having sufficiently low viscosity of the fresh mixture, so as to facilitate its flow inside Inserted Hosepipe 22 despite the constraints described above.

The length of Inserted Hosepipe 22, in the beginning of the filling process, must slightly exceed the overall height of Tower 10 being reinforced, and desirably it should be made of a continuous piece free of splices, due to the dimensional constraints described above. According to practical experience, the most commonly available hosepipe product, which is suitable to function as Inserted Hosepipe 22 when implementing the present invention, is a semi-rigid polymer hosepipe of a type used in agricultural or gardening irrigation systems. This kind of hosepipe is available in any, practically required, continuous length, and usually fulfills other dimensional, interior surface smoothness as well as pressure-bearing requirements of practical implementation. When being retracted outwards from the top of filled Primary Element 11, the already exposed part of Hosepipe 22 may prove flexible enough to facilitate handling, yet too rigid to be easily collected in hoops of considerable length, at the top of Tower 10, outside Primary Element 11. Furthermore, such hoops (of relatively small radius) may cause undesirable increase of the flow-resistance inside Hosepipe 22. Thus, it may prove to be a useful practice to make short pauses in the filling process in certain intervals, in order to cut-off the projecting portion of Hosepipe 22, and re-connect the cut top end of the remaining, substantially inserted portion, to the grout-feeding system near the top of Tower 10. This means, obviously, that Hosepipe 22 cannot be repeatedly used, yet the cost-effect of this constraint on the overall economy of implementing the present invention would prove negligible.

The above description of the desired properties of Inserted Hosepipe 22 should be regarded as merely one preferred application of the present invention, as one can easily divert to at least 2 other related applications:

in one extreme application, Hosepipe 22 is made of a totally rigid pipe, of polymer or metallic material, with sufficiently small and relatively smooth threaded splice-fittings (that in certain cases may fit into said dimensional constraints) or, in the case of metallic pipe, even welded splices made in the process of inserting the pipe into Primary Element 11 to be filled. In this application, said pauses in the filling process, to allow dismantling or cutting the projecting portion of Hosepipe 22, shall be relatively frequent.

in another extreme application, Hosepipe 22 is made of a very flexible polymer material such that, depending on the overall height of Tower 10 being reinforced, may facilitate completion of the entire filling of Primary Element 11 with grout without the necessity to make pauses in the filling process, as the entire length of the Hosepipe 22 may be collected in hoops, while retracted outwards, near the top of Tower 10, thereby causing only “bearable” negative impact on the flow of the grout inside Hosepipe 22.

The weight of Inserted Hosepipe 22, especially when it is full with the grout, may be quite heavy, thus certain auxiliary means may be required in order to support it and retracted it gradually out of Primary Element 11 being reinforced. FIG. 22 illustrates schematically one embodiment of said auxiliary means: A Hand Winch 100, equipped with compatible thin Winch Rope 101 (typically a wire rope) with length equal at least to substantially the initial length of Inserted Hosepipe 22, is fixed above Inlet Opening 16 of Primary Element 11, by means of certain conventional metal adapters (not shown). Before or during the insertion of Hosepipe 22 into Primary Element 11, the end of Winch Rope 101 is well attached to the bottom part of Hosepipe 22, near its Outlet End 105, through End Fastening Device 102, then in certain appropriate intervals Hosepipe 22 and Winch Rope 101 are further fastened to each other longitudinally, using Intermediate Fastenings 103. The selection of specific solutions for appropriate Fastening Devices 102 and 103 is significantly governed by said dimensional constraints, but also by the materials being fastened. Experience shows that high-quality adhesive tape can fulfill the function of both type Fastening Devices, where in End Fastening Device 102 increased mechanical connection between the fastened elements is achieved by spreading the wires at the end of Winch Rope 101, wrapping them around Hosepipe 22, then wrapping both with said adhesive tape along and increased continuous portion length. During the gradual retraction of Hosepipe 22, by turning Hand Winch 100, the small vertical gap between Inlet Opening 16 and Hand Winch 100 allows dismantling each Intermediate Fastening 103 as soon as it is exposed, thus allowing handling of the exposed portion of Hosepipe 22 independently from the auxiliary means described herein.

This FIG. 22 also illustrates the Bottom Sealing 106 of Primary Element 11, which must be applied in those cases where the internal cavity of said Primary Element 11 is open and accessible from the bottom, prior to commencing the grout filling process. Said Bottom Sealing 106 is most commonly carried out similarly to the original bottom sealing of such structures, namely with appropriate kind of concrete or cement grout, cast in place at least one day prior to commencing the grout filling.

For the sake of clarity and simplicity, this FIG. 22 does not illustrate other objects that may be present inside the cavity of said Primary Element 11 when the grout filling process commences, in particular it does not illustrate the Tensile Reinforcement Member, nor its bottom anchoring neither its top tensioning apparatus.

The detailed description of the invention up to this point concentrated on that part of the grout-filling system, which ensures proper transport of the grout downwards from the top of Tower 10 being reinforced, and its proper placement inside Primary Element 11, so as to achieve the desired result of a homogeneous, eventually hardened mass of filled grout, free of air cavities. Inserted Hosepipe 22 takes the key role in this part of the grout-filling system, the innovative aspect of which is the basic conceptual approach for reaching said desired result (as opposed to the approach of various techniques aiming the same result, known in the art to date).

The other part of the grout-filling system, which shall be referred herein (for convenience only) as the Grout-Feeding Subsystem, is that part of the system that handles: (a) the preparation of the grout mixture in sufficient capacity an appropriate quality, (b) the transporting the grout mixture up to substantially the top of Tower 10, and (c) ensuring said sufficient grout pressure, at the connection point between the top intake-end of Inserted Hosepipe 22 and the Grout-Feeding Subsystem. The grout pressure at said connection point shall be referred herein (for convenience only) as the Interface Point Pressure.

The practical minimal required value of the Interface Point Pressure results from the initial length of Inserted Hosepipe 22 (which substantially equals to the height of Tower 10 being reinforced), combined with the choices made by the project designer, with respect to the exact propertied of Hosepipe 22 and the type and viscosity of grout product to be used.

The Grout-Feeding Subsystem may comprise a single grout pump or a plurality of pumps, with a large variety of possible embodiments:

The simplest embodiment of the Grout-Feeding Subsystem is that where a single, high-pressure grout-pump, located at ground level, provides sufficiently high pressure to facilitate both the transport of the grout up to the top of Tower 10, and a residual pressure fulfilling the required Interface Point Pressure. In this embodiment, that is illustrated schematically in FIG. 1, Bottom Grout Pump 24, which is a high-pressure grout-pump (typically of a type readily available in the market), is located at ground level, near a Grout Mixing Device 25. Some machines available in the market offer the convenience of combining Grout Pump 24 and Grout Mixing Device 25 in that single machine. Exterior Grout Pipe 27, which is typically a flexible, high pressure hose available in the market as an accessory of Bottom Grout Pump 24, but may also be made of a tailored, rigid metallic pipe-line, serves the transport of the grout up to substantially the top of Tower 10. The bottom end of Exterior Grout Pipe 27 is connected to Outlet Stub 26 of Pump 24, and its top end is connected to the top intake-end of Inserted Hosepipe 22, through a Step-Down Hose-Coupler 28 and complementary fittings, part or all of which may be readily available in the market or specially fabricated, depending on the specific cross-sectional dimensions of Pipe 27 and Hosepipe 22. The Interface Point Pressure is the residual grout pressure at Hose-Coupler 28, which is obviously much lower than the output pressure of Pump 24 (measurable at Outlet Stub 26), yet it must be sufficient to facilitate the further transport of the grout along the entire length of Inserted Hosepipe 22. In actual implementation, needless to say, Exterior Grout Pipe 27 is mechanically connected to Tower 10 in certain points along its height, so as to support its weight and to ensure it is kept substantially straight.

Another rather simple, yet very different embodiment of the Grout-Feeding Subsystem is that, where said Interface Point Pressure, required to ensure the transport of the grout along the entire length of Inserted Hosepipe 22, is provided by a low-pressure Top Grout Pump 21, located near the top of Tower 10 being reinforced, and is schematically illustrated in FIG. 2. Top Grout Pump 21, which, may be an electrically motored pump or a manually driven one, will be selected by the project designer based on its output pressure (that must exceed the minimal required value of said Interface Point Pressure), as well as on other relevant properties, such as minimal operational vibration and relatively low flow capacity. Top Grout Pump 21 requires a constant intake flow of grout—that's the role of Buffer Tank 20, which must therefore be located slightly above Top Grout Pump 21, at the top part of the tower. Most existing towers or similar structures would be large enough at the top, and even have certain work-platforms, which would ease the placement of both Buffer Tank 20 and Top Grout Pump 21. In other cases, temporary ancillary structures may need to be fitted for this purpose. These would all be specific conventionally engineered solutions, tailored to the case, therefore FIG. 2 shows the location of said equipment near the top part of Tower 10 only in a schematic manner.

In conjunction with the above embodiment of the Grout-Feeding Subsystem, there are also various embodiments for the “feeding” Buffer Tank 20, i.e. securing the supply of required volume of fresh grout mix into it, in appropriately timed batches or in a constant flow:

-   -   mixing the grout near the location of Buffer Tank 20 (at the top         part of the structure)—this may be suitable in those cases where         Tower 10 is sufficiently robust, and can sustain the vibration         caused by mixing operations without substantial dynamic         oscillation;     -   mixing the grout substantially at ground level (as illustrated         in FIG. 2 by the location of grout-mixer 25) and lifting the         ready grout mix in batches (buckets), utilizing any one of many         practices exercised conventionally in the construction industry;     -   mixing the grout substantially at ground level and pumping the         ready grout mix up to Buffer Tank 20, using a high pressure         grout pump such as Bottom Grout Pump 24, in timed batches or in         a continuous flow—this practice may prove practical where the         output pressure of Bottom Grout Pump 24 is sufficient for         transporting the grout up to the top of Tower 10, but the         residual Interface Point Pressure is too small, and would not         ensure the further transport of the grout along the entire         length of Inserted Hosepipe 22.

None of the solutions set forth above is illustrated in detail on schematic FIG. 2, yet the later two general applications, which involve mixing at ground level, are represented by Grout Mixing Device 25 being shown at ground level, and a series of arrows pointing upwards, representing the transport of the ready grout mixture up to Buffer Tank 20, in any of the methods described above.

During the entire process of filling a single Hollow Primary Element 11 with grout, Buffer Tank 20 may be filled and emptied, fully or partly, in a plurality of cycles, while Hosepipe 22 is gradually retracted upwards through Inlet Opening 16, at a pace that matches the raise of the grout level within Hollow Primary Element 11.

The simpler group of applications, for the slow and low-pressure grout-filling method disclosed herein facilitates the filling of Primary Elements 11 one at a time, in a sequential order (unlike the application shown in FIG. 2). In this group of applications, at any given time only a single Inserted Hosepipe 22 is connected directly to the Grout-Feeding Subsystem.

Pouring the Grout into the respective Hollow Primary Element 11 through Inserted Hosepipe 22, is driven by the Grout-Feeding Subsystem at such a slow pace (including possible planned pauses), that ensures that the height of the fresh Grout (i.e. the not yet hardened grout) within the Primary Element 11 does not exceed a predetermined value. This fresh grout height limitation is aimed to ensure that the hydrostatic pressure affected by the grout upon the walls of Hollow Primary Element 11 is kept well within a safe range, therefore it is to be determined by the structural designer, based on the specific physical properties of the existing Primary Element 11.

Following the complete filling of the first Hollow Primary Element 11 with grout, up to the prescribed final level (which in most practical cases would be up to the top of Primary Element 11), the same filling procedure is repeated in each of the other Hollow Primary Elements 11, in a sequential order.

This simpler group of applications, as described above, suits particularly those cases, where the cross-sectional area of a single Primary Element 11 is rather big, and therefore the allowable grout flow capacity, into a single Primary Element 11, is a relatively high capacity. In most real cases, however, involving Primary Elements 11 with ordinary cross-sectional area, this group of applications might prove to be too slow, as the safe pace of grout-filling will be quite slow, and will result in too high proportion of idle time (that could be used meanwhile to gradually fill the other Hollow Primary Elements 11 in parallel).

Hence, another group of applications of the slow and low-pressure grout-filling method, disclosed in the present invention, facilitates the grout-filling of a plurality (preferably all) of Hollow Primary Elements 11 in parallel, almost simultaneously, thereby substantially reducing idle time and expediting the entire reinforcement task (this application resembles the one shown in FIG. 2, but it does not include the Multi-Valve Distribution Block 23 that is shown in FIG. 2). In this group of applications, a plurality of Inserted Hosepipes 22 is used in parallel, such that each of Hollow Primary Elements 11 has one Hosepipe 22 inserted and lowered there into. In this group of applications, the top intake end of each of said Inserted Hosepipes 22 is connected directly to the outlet end of the Grout-Feeding Subsystem (namely to Step-Down Hose-Coupler 28 or to the outlet of Grout Pump 21) only for a relatively short duration at a time, facilitating only partial filling of the respective Hollow Primary Element 11, following which another Inserted. Hosepipe 22 is connected to said outlet end of the Grout-Feeding Subsystem only for a short duration to facilitate similar partial filling of the other respective Hollow Primary Element 11, and this procedure is repeated with all Inserted Hosepipes 22 in a sequential and cyclic manner, maintaining the Grout level differences between the various Hollow Primary Elements 11 within a predetermined value, until the grout level in all Hollow Primary Elements 11 has reached the prescribed final levels.

In yet another group of applications of the slow and low-pressure grout-filling method disclosed herein (and one particular shown in FIG. 2), the same effect of parallel, almost simultaneous grout-filling of a plurality (or all) of Hollow Primary Elements 11 is achieved at a higher comfort and speed by the utilization of a Multi-Valve Distribution Block 23. The number of valves in Multi-Valve Distribution Block 23 is equal (or exceeding) the number of Hollow Primary Elements 11 to be filled with Grout substantially simultaneously. Multi-Valve Distribution Block 23 is connected (directly, or through a short hose) to the outlet of Grout Pump 21, and the top intake end of each of said Inserted Hosepipes 22 is connected to one respective valve in said Block 23. Multi-Valve Distribution Block 23 facilitates either simultaneous flow of the grout into all respective Hollow Primary Elements 11, or only into one of them at any given short duration, in a sequential cyclic manner as it would be done according to the previous group of applications, yet faster and more comfortably. The routing of the grout into any desired Hollow Primary Element 11 is controlled by easy valve-switching, avoiding the time-consuming effort of disconnecting and re-connecting the top intake end of each of Inserted Hosepipes 22 to the outlet end of the Grout-Feeding Subsystem, too many times repeatedly.

Even though the internal pressures produced in the filling process are intentionally kept relatively low, the entire Hollow Primary Elements 11 must be watertight before the grout filling can start, save for the top Inlet Opening 16. Sealing the bottom gaps between the steel structure and the concrete foundation is conventionally performed by earlier grouting. Sealing any other potential leaking points, such as possible small gaps between abutting flanges 12, is conventionally performed with the use of elastomeric materials.

An improved version of any of the applications disclosed above is obtained through the utilization of a specialized Remote Portable Camera System, which facilitates visual monitoring of the grout-filling process so as to verify that it is free of any unforeseen obstructions. The Camera (or plurality of cameras, respectively), which forms part of said System, is appropriately small and durable, has an integrated flashlight, and is lowered into the respective Hollow Primary Element 11 through Inlet Opening 16 together with the respective Inserted Hosepipe 22, so as to provide a real-time, close-range electronic image of the filling process. Hence, said Camera (or each of said cameras, respectively) is also retracted upwards together with the respective. Inserted Hosepipe 22, so as follow the rise of the grout level.

A further improved version of any of the applications disclosed above is that, in which said Remote Portable Camera System facilitates also recording of the video signals obtained through the camera (or plurality of cameras), thus the entire said Grout-filling process may be electronically-documented.

Referring now to the methods for improving the tensile load-bearing capacity of the structure's Primary Elements, it will be acknowledged, that while these tensile reinforcement methods can only be implemented in conjunction with grout-filling of the Hollow Primary Element 11 being reinforced, they do not depend on the specific grout-filling method being implemented, namely they are as valid when the grout filling is done in accordance with the present invention, as when it is done through high-pressure injection from the bottom upwards following prior art practices.

FIG. 3 illustrates a very simple application of such a method, owing to the fact that the Primary Elements 11 are totally straight, top to bottom. The method for increasing the tensile load bearing capacity of Hollow Primary Elements 11, which is to be used in conjunction with their filling with grout, comprises:

-   a. Preparing a respective required quantity of a longitudinal,     continuous Tensile Reinforcement Member 30, made of steel and having     a Bottom End Fitting 51 designed to engage a respective Bottom     Anchoring Apparatus 50, said Bottom End Fitting 51 being     sufficiently small to pass through the respective top Inlet Opening     16 and through the narrowest part of the internal cavity of the     respective Hollow Primary Element 11; -   b. Preparing a respective required quantity of Top Tensioning     Apparatus 60, each tailored to fit the respective typically existing     top flange 15 or another existing connecting apparatus near top     Inlet Opening 16 of the respective Hollow Primary Element 11, and     constructed in a way that would not obstruct the insertion of the     Tensile Reinforcement Member 30 into said respective Hollow Primary     Element 11, and where applicable: would also facilitate the handling     (namely insertion and retracting) of the Inserted Hosepipe 22,     through which said grout-filling may take place; -   c. Inserting each of said Tensile Reinforcement Member 30 into the     respective Hollow Primary Element 11, until its respective Bottom     End Fitting 51 reaches the bottom of the respective Primary Element     11, and its top end is suspended from said Top Tensioning Apparatus     60; -   d. Installing and fixing the complete Bottom Anchoring Apparatus 50     between the bottom part of the respective Hollow Primary Element 11     and the Bottom End Fitting 51 of the respective Tensile     Reinforcement Member 30; -   e. Applying an axial pretension of predetermined magnitude to said     respective Tensile Reinforcement Member 30, through said Top     Tensioning Apparatus 60; -   f. Filling the entire internal cavity of said respective Hollow     Primary Element 11, or any part thereof as prescribed by the     structural designer, with cement-based non-shrink Grout.

The tensioning device within said Top Tensioning Apparatus 60 may be a conventional turnbuckle 61, as illustrated in FIG. 3, or alternatively, as illustrated in FIG. 4, may comprise a threaded rod 62 passing, substantially vertically, through a rigid top cover plate of Top Tensioning Apparatus 60, such that the tensioning is applied by tightening of a top Tensioning Nut 63 over said threaded rod 62.

According to a rather simple embodiment for Tensile Reinforcement Member 30, it is made of a plurality of long steel Rods (such as rod 31 on FIG. 5) all of which having substantially equal cross-section, each of said Rods having threaded end portions (34, 35 on FIG. 5) at both its ends, a plurality of Threaded Couplers (81 on FIG. 5) equipped with matching internal threads, and a Bottom End Fitting 51 (not shown in FIG. 5) equipped with matching internal thread as well. The process of installing said Tensile Reinforcement Member 30 starts with mounting said Bottom End Fitting 51 onto the bottom thread of the bottom-most of said steel Rods, then all said steel Rods 31 are sequentially coupled to each other, through said Threaded Couplers 81, during the process of inserting the Tensile Reinforcement Member 30 into the respective Hollow Primary Element 11.

In an optimized design though, a substantially constant proportion should be maintained between the cross-sectional area of the original Hollow Primary Element 11 and that of the Tensile Member 30 meant for its reinforcement. In the case of an ordinary tower structure 10, in which the original cross-sectional area of the leg is normally decreasing in a stepped manner, from the bottom upwards, the cross-sectional area of the Tensile Reinforcement Member 30 should preferably also step down gradually. Another reason that may necessitate this gradual variation in the cross section of the Tensile Reinforcement Member, is the space constraints within Hollow Primary Element 11 (the tower leg in this case): Throughout the length of Primary Element 11, certain clearance must be maintained between the central Tensile Reinforcement Member 30 and the inner wall of Primary Element 11. In most cases, this constraint sets a stringent limit on the “allowable” maximal diameter of Tensile Reinforcement Member 30 in the upper portion of Primary Element 11. At the same time, the cross-section of the Tensile Reinforcement Member 30 at the bottom section must be large enough, so as to ensure the mentioned reasonable proportion with the cross-section of Primary Element 11 at that bottom part. Hence, the only way to harmonize these two conflicting constraints is to produce a Tensile Reinforcement Member 30 with a varying cross-sectional area, largest at the bottom part and decreasing gradually towards the top.

Accordingly, in another embodiment of Tensile Reinforcement Member (30), which is illustrated in FIG. 5, it is made of a plurality of long steel Rods (31 through 33) made in several different cross-sectional dimensions, each of said Rods (31 through 33) having threaded end portions (34 through 39) at both its ends, a plurality of Threaded Couplers of several matching sizes (81, 82) equipped with matching internal threads, and a Bottom End. Fitting 51 (not shown in FIG. 5) equipped with internal thread matching the bottom thread 39 of the bottom-most Rod. The number of Rods (31 through 33) may be larger than the number of different cross-sectional dimensions, such that a plurality of said rods may be of similar cross-section. Rods (31 through 33) make up a complete Tensile Reinforcement Member 30 such that its bottom portion is made of the largest cross-section Rods 33, and the cross-sections are stepping down in certain designed step-down coupling locations, wherein the top-end thread (36, 38 respectively) of the lower joining Rod (32, 33 respectively) is made smaller than the typical size thread (37, 39 respectively) of the respective Rod, so as to match the smaller size thread of the joining Coupler (81, 82 respectively), which in turn matches the thread (35, 37 respectively) of the upper joining Rod (31, 32 respectively). The process of installing said Tensile Reinforcement Member (30) in the case of this embodiment is very similar to that described for the previous embodiment.

Making Tensile Reinforcement Member 30 of a stiff continuous steel rod (once assembled), as disclosed in the previous embodiments, may prove to be the most cost-effective choice, especially when the axis of the Primary Element 11 being reinforced (in the case of a tower: the axis of the tower leg) is arranged along a straight line throughout its length. However where said axis is not straight (as is the typical case with most self-supporting telecom towers, where said axis has a break-point between a vertical-legged top portion and an inclined-legged structure underneath it), in certain cases the insertion of such a stiff rod, fulfilling a required cross-sectional area, from the top of said Primary Element 11 downwards, might not be feasible. In those cases Tensile Reinforcement Member 30 should preferably be made of a steel strand.

Hence, according to a rather simple embodiment of Tensile Reinforcement Member 30, it is made of a single continuous Steel Wire Strand or Wire Rope, of uniform cross-section throughout its length, and is equipped with a Bottom End Fitting 51 engineered and mounted onto its bottom end according to any common practice known in the wire rope industry.

The stepped variation of the cross-sectional area of said Tensile Reinforcement Member 30, as described above, may be a requirement, or even a constraint, also when it is made of a Steel Wire Strand or Wire Rope.

Accordingly, another embodiment of the Tensile Reinforcement Member 30, which is shown in FIG. 4, is making Tensile said Reinforcement Member of several segments of a Steel Wire Strand or Wire Rope (41 through 43), each made with a different cross-section, the bottom, thickest segment 43 is equipped with a Bottom End Fitting 51, engineered and mounted onto its bottom end according to any common practice known in the wire rope industry, and the other segments (42, 41) being coupled with each other and with the thickest segment 43 in a cross-sectional stepping down sequence, with splicing means (71, 72) based on any common practice known in the wire rope industry.

According to yet another embodiment of the Tensile Reinforcement Member 30, which is shown in FIG. 6, it is made of a single continuous Steel Wire Strand, the cross-section of which consists of several layers of wires arranged in concentric circles, said Tensile Reinforcement Member 30 being divided into a plurality of segments (141 through 144), the cross-sectional dimensions of said segments stepping-down respectively. The stepping-down of the Wire Strand's cross-sectional dimensions is obtained by peeling off a layer of the wires at each stepping down point, such that the cross-section of the bottom-most segment is equal to the Wire Strand's original cross-section, and the upper-most segment has the largest number of wire layers peeled off. Said Tensile Reinforcement Member 30 further including a Bottom End Fitting 51 (not shown in FIG. 6) engineered and mounted onto the bottom end of the bottom segment 144 according to any common practice known in the wire strand industry. A recommended complementary measure for preventing undesired local deterioration of the Strand's structure at the cross-sectional step-down locations, during winding and handling, includes protecting metal sleeves 149, of appropriate dimensions, fitted and crimped onto the Wire Strand at these locations.

When the longitudinal axes of all or part of the Hollow Primary Elements 11 of the existing structure have a breaking (turning) point at a certain intermediate location along their height, certain additional provisions must implemented so as to ensure that the axis of Tensile Reinforcement Member 30 is maintained substantially concentric with that of the respective Hollow Primary Element 11. According to an application of the present invention, illustrated in FIG. 4, said provisions include a sufficient number of Restrainer 90, each being mounted onto a respective Hollow Primary Element 11 at a location close to said axial breaking point, after cutting or drilling an appropriate small opening through the wall of respective Primary Element 11 at said location, each said Restrainer 90 being shaped and sized so as to hold Tensile Reinforcement Member 30 substantially concentric with surrounding Hollow Primary Element 11.

FIGS. 20 & 21 illustrate one embodiment of said Restrainer 90, according to which it comprises an Insert 150 inserted into the respective Hollow Primary Element 11 through a hole 160 drilled in its wall, such that Insert 150 is designed to stay permanently within the reinforced structure. In this embodiment, Restrainer 90 further comprises temporary, removable and reusable supporting and fastening means, mounted on the exterior of the respective Hollow Primary Element 11, designed to firmly hold Insert 150 in place inside said Primary Element 11 during the entire grout-filling process. The length of insert 150 is determined so as to restrain Tensile Reinforcement Member (41 in FIGS. 20, 21) in the designed, substantially concentric location, and its free end is shaped with an alcove matching the cross-section of Tensile Reinforcement Member (41). The rear end of Insert 150 is equipped with a threaded bore 158, so as to facilitate connection to said temporary supporting and fastening means by a removable bolt 155. In the illustrated embodiment, said temporary supporting and fastening means comprise a clamping device fitted to the cross-section of Primary Element 11, made commonly of 2 parts 151 & 152, bolted to each other with bolts 153 and nuts 154, one respective part of the clamp 151 having a drilled hole with a location and size matching those of said threaded bore 158 in Insert 150, and said bolt 155 which secures Insert 150 onto said clamp 151.

When the Existing (tower) Structure 10 is fastened down to its concrete foundation with substantially vertical Anchor Bolts (14 in FIG. 4), in most cases the bottom ends of its Primary Elements 11 are formed as Base Flanges (13 in FIG. 4), with holes through which said Anchor Bolts 14 pass through. In most such cases said Base Flanges 13 are shaped so that Primary Element 11 is left entirely open at its bottom. Furthermore, with this type of anchoring system, the common practice (during the original construction of said Structure 10) is to locate Leveling Nuts (18 in FIG. 8) under said Base Flanges 13, in order to facilitate post-erection adjustment of the verticality of the entire Structure 10. As a consequence of this practice, there is a certain Vertical Gap between the concrete foundation and said Base Flanges 13. (In good practice, this Vertical Gap is sealed with an appropriate concrete or grout layer, after verticality is verified in the original construction phase, but this layer can be fairly easily dismantled at any later stage). Certain embodiments of said Bottom Anchoring Apparatus 50, through which the Bottom End Fitting 51 of Tensile Reinforcement Member 30 is anchored to the base of Hollow Primary Element 11, take advantage of said Vertical Gap between the concrete foundation and said Base Flanges 13.

In a rather simple embodiment of said Bottom Anchoring Apparatus 50, which is illustrated in FIGS. 7, 8 & 9, said Bottom Anchoring Apparatus 50 is designed as a simple, monolithic Beam 180 with a height not exceeding said Vertical Gap and a length sufficiently larger than the bottom opening in Base Flange 13, and said Bottom End Fitting 51 is shaped uniquely as a Fitting 181 equipped with a horizontal bore substantially transverse to its longitudinal axis, shaped and dimensioned to facilitate the passage of Beam 180 there through, with good dimensional fit there between. Said Beam 180 must have sufficient bending-load-bearing capacity considering its bending span and the sustained load of Tensile Reinforcement Member 30.

The bottom portion 44 of Tensile Reinforcement Member 30 is shown on these FIGS. 7, 8 & 9, as well as on the following figures, as being made of a steel strand or wire rope, but it should be noted that all these figures remain as valid also in the case that said Tensile Reinforcement Member 30 is made of rigid rods (an embodiment of which is illustrated in FIG. 5).

In another embodiment of said Bottom Anchoring Apparatus 50, which is designed for similar existing structure circumstances as the previous embodiment and is illustrated in FIGS. 10, 11 & 12, Bottom End Fitting 51 comprises a top part 110 mounted onto the bottom end of respective Tensile Reinforcement Member 44 and heaving a substantially vertical threaded bore at its bottom, and a bottom part 111 which is a matching bolt, possibly having a specially shaped head. In this embodiment, said Bottom Anchoring Apparatus 50 comprises a longitudinally & vertically split beam consisting two parts 112 & 113, which may be identical or differ in shape, each containing a shaped groove, such that when the beam consisting the two parts 112 & 113 is assembled, it snugly houses the head-part of bolt 111. The height of each beam part (112, 113) does not exceed said Vertical Gap, its length being sufficiently larger than the bottom opening in Flange 13, and the two parts 112 & 113 are secured to each other after assembly with bolts 114 and nuts 115.

In yet another embodiment of said Bottom Anchoring Apparatus 50, which is designed for similar existing structure circumstances as the previous two embodiments and is illustrated in FIGS. 13, 14 & 15, said Bottom End Fitting 51 is shaped as a Fitting 120 having two parallel flat faces on both its sides and a through-passing smooth bore with an axis substantially perpendicular to said two parallel flat faces and to the axis of the Tensile Reinforcement Member 44, and said Bottom Anchoring Apparatus 50 comprises two substantially identical beams 121, clamping said End Fitting 120 there between. Each of said beams 121 is made of a steel plate positioned vertically, having a transverse through-passing smooth bore matching in size said bore of End Fitting 120, and shaped such that its central portion may be somewhat higher than said Vertical Gap (so as to increase flexural resistance while fulfilling the dimensional constraints facilitating their installation). Said Bottom Anchoring Apparatus further comprises a relatively thick Connecting Pin 122, dimensioned to sustain the expected shear loads and long enough to secure both beams 121 onto End Fitting 120, machined smooth along its central portion and with smaller diameter threads on both ends, so as to facilitate tightening with one or two nuts 123 and washers 124 that are larger than said smooth bores. This embodiment is especially suitable for those cases where the axis of Primary Element 11, and consequently the axis of Tensile Reinforcement Member 44 is inclined and not perpendicular to the plane defined by the underside of Base Flange 13, as the pivot-effect defined by Connecting Pin 122 facilitates simple adjustment to the actual angle between said axis and said plane, without necessarily knowing the exact value of said angle beforehand, and regardless of possible fabrication inaccuracy with respect to said angle.

According to another embodiment, which branches from the previous one and therefore presents similar advantages to those described above, said Connecting Pin 122 does not have said smaller diameter threads at its ends, and said clamping of said End Fitting 120 between said two plate beams 121 is secured by separate, at least two long bolts, passing transversely through both said plate beams 121 without contacting said End Fitting 120, such that tightening said separate long bolts ensures that both plate beams 121 tightly abut said two parallel flat faces on both sides of End Fitting 120, while said Connecting Pin 122 is positioned in said through-passing smooth bores of said End Fitting 120 and of both said plate beams 121.

In certain cases of an Existing Lattice Structure 10, the bottom ends of said existing Hollow Primary Elements 11 are constructed such, that access to the bottom of their interior cavities is not facilitated. In other cases it may be the project designer's choice not to utilize such access possibilities (from underneath the structure). In these cases, the bottom anchoring of Tensile Reinforcement Member 30 must be solved otherwise. According to one embodiment of such a solution, which is illustrated in FIGS. 16, 17 & 18, said Bottom Anchoring Apparatus 50 is designed as a simple Beam 132, passing transversely through said existing Hollow Primary Element 11, after cutting on site two openings in its walls in appropriate sizes and locations. Optional reinforcing of the cut openings by welded plates (133, 134), in one or more layers, may be utilized. The field cuttings might be rough and the resulting openings too large, but said reinforcing plated (133, 134) may have shop-machined openings, matching the cross-sectional shape of Beam 132, thus ensuring a tight fit there between. Said Bottom End Fitting 51 of the Tensile Reinforcement Member 44 is shaped uniquely as a Fitting 131 equipped with a horizontal transverse bore shaped and dimensioned to facilitate the passage of beam 132 there through, with a good geometric fit there between. Said Beam 132 must have sufficient bending-load-bearing capacity considering its bending span and the sustained load of Tensile Reinforcement Member 30.

One can appreciate, that said Tensile Reinforcement Member 30 does not necessarily have to be made of either a rigid rod in its entire length, or alternatively of a relatively flexible steel strand or wire rope in its entire length. Embodiments in which Tensile Reinforcement Member 30 is made of a combination of steel rods and wire strands or wire ropes, in various segments, spliced together so as to make up a complete continuous tensile member can be implemented as well as applications of the present invention.

The tensile load capacity of the anchoring system of Existing Structure 10, which connects between the bottom ends of said Primary Elements 11 and the concrete foundation, may in some cases also reach exhaustion and fall short of fulfilling the required increased anchoring load capacity of the reinforced structure. In such a case, said anchoring system may also be reinforced, by one of many possible procedures commonly practiced in the art. FIG. 19 illustrates one such possible procedure, which includes welding appropriate, substantially horizontal steel plates 204, having a required number of holes for additional anchoring bolts 200, onto the bottom end of said Primary Element 11, then drilling into the concrete foundation, and installing with the utilization of appropriate epoxy resin (201) or the like, a required number of additional anchor bolts 200, tightening the nuts (203) of said additional anchor bolts (200) after said resin (201) has cured, and possibly encasing the entire reinforced base in a protective mass of non-shrink concrete 202. While the present invention concentrates specifically on the reinforcement of the Primary Elements 11 of the Existing Structure 10, in many practical cases the entire reinforcement task may also require improving the load bearing capacity of certain secondary elements of the Existing Structure 10, namely of certain lattice brace members (these are the diagonal and horizontal members position between said Primary Elements 11). This complementing task may be carried out through the implementation of one of many possible procedures commonly practiced in the art. In most real cases the Existing Structure 10 is a bolted structure, and the simplest and most common procedure is the replacement of said certain lattice brace members with new brace members, having larger cross-sectional area, and/or other improved properties.

The present invention presents a series of related, efficient and cost-effective methods for reinforcing existing lattice frame structures having substantially vertical hollow steel primary elements, particularly reinforcing steel lattice towers with tubular legs.

The invention presents two main groups of innovative methods for executing said reinforcement task, which may be combined with each other, or applied separately:

The first group of said innovative methods facilitates the increase of the compressive load-bearing capacity of the substantially vertical hollow steel primary elements of the existing structure, through filling their cavities of with non-shrink cement-based grout in as slow pace as desired, so as to ensure that the hydrostatic pressures of the grout, applied internally upon the walls of said hollow primary elements, do not exceed a desired, possibly low value, predetermined by the structural designer.

The second group of said innovative methods facilitates the increase of the tensile load-bearing capacity of all, or any part of said primary elements, through the insertion, prior to the grout-filling, of a longitudinal, continuous and substantially concentric tensile reinforcement member into each respective primary element, and anchoring it properly to the bottom of said primary element. An axial pretension of predetermined magnitude is applied through a top tensioning apparatus, which also fixes the top end of said tensile reinforcement member during the grout-filling process and at least until the grout is cured and hardened. The grout filling procedure itself may follow a method disclosed by the present invention, or any other prior art technique.

One important advantage of the grout-filling methods disclosed by the present invention is the applicability of said methods to practically any existing steel structure with hollow primary elements, regardless of the capacity of said primary elements to withstand internal pressure. This advantage is particularly important in the case of certain typed of existing structures, especially where said hollow primary elements are made of longitudinally seamed pipes of relatively large diameter and small wall-thickness, due to the limited capacity of such elements to sustain such internal pressures, which might rule out the feasibility of grout-filling through any prior art technique, as all such prior art techniques involve the build-up of high internal pressures.

Another important advantage of the grout-filling methods disclosed by the present invention, compared to all prior art techniques for grout-filling, which are considered to be fairly complicated and risky, and necessitate the use of costly specialized equipment and the application of equipment break-up plan (which means additional back-up equipment), and therefore they must be carried out exclusively contractors having the necessary experience and equipment, while the methods disclosed by the present invention are far less risky, and do not necessarily require very costly equipment and back-up plan.

An advantage presented by the optional utilization of Multi-Valve Distribution Block 23, is that it facilitates either simultaneous flow of the grout into all respective Hollow Primary Elements 11, or routing it only into one of them at any given short duration, in a sequential cyclic manner, switching between them quickly and comfortably. The routing of the grout into any desired Hollow Primary Element 11 is controlled by easy valve-switching, avoiding the (otherwise required) time-consuming effort of disconnecting and re-connecting the top intake end of each of Inserted Hosepipes 22 to the outlet end of the Grout-Feeding Subsystem, too many times repeatedly.

An important advantage of the possible combination of methods disclosed by the present invention is, that they offer the designer the option to choose between improving only the compressive load-bearing capacity of the existing structure's primary elements, or improving both the compressive and the tensile load-bearing capacities of said primary elements. Obviously, the improvement of both the compressive and the tensile load-bearing capacities involves a higher level investment, yet it will prove inevitable in those structures where the existing primary elements might be overstressed by expected tensional loads. In other structures, the primary elements might come under overstressing only by the expected compressive loads, and the problem may be solved at a lower level of investment. Hence, an optimized reinforcing solution may be tailored by the structural designer, considering the specific characteristics of the specific structure.

Yet another important advantage of the methods disclosed by the present invention, in the context of reinforcing Telecom Network towers, is that the reinforcing work may take place without necessitating the temporary removal of antennas from the tower, hence no interruption of services is required, compared to alternative reinforcing methods that involve welding or mounting reinforcing elements onto the exterior of said Hollow Primary Elements, in which case said temporary removal of antennas might be inevitable.

LIST OF REFERENCES

-   10—Existing Structure (Lattice Tower with tubular legs is     illustrated) -   11—Hollow Primary Element(s) (of the existing structure) -   12—Tower leg splice(s) (of the existing structure), made of welded     bolting flanges -   13—Base Flange(s) (of the existing structure) -   14—Anchor Bolt(s) (of the existing structure) -   15—Top Flange(s) (of the existing structure) -   16—Inlet Opening(s) -   17—Anchor bolt holes in the base flange -   18—Leveling nut(s) (of Anchor bolts) -   19—Securing nut(s) (of Anchor bolts) -   20—Buffer Tank -   21—Top Grout Pump, which is a low-pressure grout pump placed near     the top of the existing structure -   22—Inserted Hosepipe(s) -   23—Multi-Valve Distribution Block -   24—Bottom Grout Pump, which is a high-pressure grout pump placed at     ground level -   25—Grout Mixing Device -   26—Outlet Stub (of Bottom Grout Pump) -   27—Exterior Grout Pipe -   28—Step-Down Hose-Coupler -   30—Tensile Reinforcement Member -   31, 32, 33—Steel Rod with threaded ends (used to make Tensile     Reinforcement Member) -   34, 35, 36, 37, 38, 39—Threaded end portion of steel rod -   41—A Segment of Tensile Reinforcement Member, made of Steel Wire     Strand or Wire Rope -   42—Intermediate Segment of Tensile Reinforcement Member, made of     Steel Wire Strand or Wire Rope -   43—Bottom Segment of Tensile Reinforcement Member, made of Steel     Wire Strand or Wire Rope -   44—Tensile Reinforcement Member (bottom portion thereof) -   50—Bottom Anchoring Apparatus -   51—Bottom End Fitting (of the Tensile Reinforcement Member) -   60—Top Tensioning Apparatus -   61—Turnbuckle -   62—Threaded rod (of Top Tensioning Apparatus) -   63—Tensioning Nut (of Top Tensioning Apparatus) -   71, 72—Splicing means for steel wire strand or wire rope -   81, 82—Threaded Couplers -   90—Restrainer -   100—Hand Winch -   101—Winch Rope -   102—End Fastening Device (between Winch Rope and Inserted Hosepipe) -   103—Intermediate Fastening (between Winch Rope and Inserted     Hosepipe) -   105—Outlet End (namely bottom end of Inserted Hosepipe) -   106—Bottom Seal of Hollow Primary Element, placed prior to grout     filling -   110—Threaded end fitting (forming part of Bottom End Fitting) -   111—Bolt, possibly with a shaped head (forming part of Bottom End     Fitting) -   112, 113—The parts of a longitudinally & vertically split beam     forming a Bottom Anchoring Apparatus -   114—Securing bolt -   115—Securing nut -   120—Bottom End Fitting (having a through-passing bore with, an axis     substantially perpendicular to the axis of the Tensile Reinforcement     Member) -   121—Beam(s), relatively thin, possibly with higher middle portion     (forming a Bottom Anchoring Apparatus) -   122—Connecting Pin (between Bottom End Fitting & Bottom Anchoring     Apparatus) -   123—Tightening nut -   124—Large Washer -   131—Bottom End Fitting -   132—Beam (forming a Bottom Anchoring Apparatus) -   133, 134—Reinforcing plates (around new openings to be cut on site) -   141—Top segment of a continuous wire strand Tensile Reinforcement     Member -   142, 143—Intermediate segment of a continuous wire strand Tensile     Reinforcement Member -   144—Bottom segment of a continuous wire strand Tensile Reinforcement     Member -   149—Protecting metal sleeve (for wire strand's cross-sectional     step-down points) -   150—Insert (forming part of Restrainer) -   151, 152—Clamp serving as Temporary Supporting and Fastening Means     (forming part of Restrainer) -   153—Bolt for securing Clamp -   154—Securing nut -   155—Bolt (for connecting Restrainer's Insert) -   158—Threaded bore in Insert (to receive connecting bolt) -   160—Opening drilled or cut on site in wall of Hollow Primary Element     (to facilitate installation of Restrainer) -   180—Bottom Anchoring Apparatus (one embodiment thereof) -   181—Bottom End Fitting of the Tensile Reinforcement Member (one     embodiment thereof) -   200—Additional anchoring bolts installed into the existing     foundation (for reinforcing the existing structure's anchoring     system) -   201—Epoxy resin -   202—Encasing concrete -   203—Nuts of additional anchoring bolts -   204—Substantially horizontal steel plates, welded onto the bottom     end of the Hollow Primary Element, as part of reinforcing its     anchoring system to the foundation -   213—Bottom flange of existing Hollow Primary Element -   214—Top flange of existing structure's foundation anchoring     structure -   215—Main anchoring bar of existing structure's foundation anchoring     structure -   216—Existing bolts connecting base of said Primary Element and the     foundation anchoring structure 

1. A method for reinforcing an existing lattice frame steel structure or tower (10) having substantially vertical Hollow Primary Elements (11), by filling the continuous longitudinal cavities of said Hollow Primary Elements with a non-shrink cement-based Grout, in a slow and low-pressure procedure, and in a sequential order, wherein said method comprises: a. Gaining access to said continuous longitudinal cavity of said respective Primary Element (11) through an Inlet Opening (16) located at its top, either by removing a cap plate or another bolted element sealing said existing Inlet Opening (16), or otherwise cutting or drilling such Inlet Opening through the top of said Primary Element (11) to be reinforced; b. Lowering an Inserted Hosepipe (22) into each respective said Primary Element (11) to be reinforced, through said respective Inlet Opening (16), each of said Inserted Hosepipe (22) being long enough to reach substantially the bottom of said respective Hollow Primary Element (11), such that a relatively short part of said inserted Hosepipe (22) projects outward from the top of respective Primary Element (11); c. Sealing (in as much as necessary) any openings at the bottom of said Hollow Primary Elements (11) or at any higher point, through which the grout might leak out, except for the Inlet Opening (16); d. Preparing a Grout-Feeding Subsystem comprising: (i) A Bottom Grout Pump (24), which is a high-pressure grout-pump (typically of a type readily available in the market), located at ground level, near a Grout Mixing Device (25) (also typically of a type readily available in the market). Grout Pump (24) and Grout Mixing Device (25) may be combined in the same machine; and (ii) A substantially vertical Exterior Grout Pipe (27), which is typically a flexible, high pressure hose available in the market as an accessory of Bottom Grout Pump (24), but may also be made of a tailored, rigid metallic pipe-line, laid between Bottom Grout Pump (24) and substantially the top of the Structure (10) being reinforced, its bottom end being connected to Outlet Stub (26) of Pump (24), and its top end being connected to one of the top intake-ends of said Inserted Hosepipes (22), through a Step-Down Hose-Coupler (28), fitted to engage the larger cross-section of Grout Pipe (27) on one side, and the smaller cross-section of Hosepipe (22) on the other; e. “Feeding” said Bottom Grout Pump (24) with appropriate volume of fresh Grout mix, prepared using said Grout Mixing Device (25) in timed batched, as necessary to match the pace of the Grout filling process; f. Pumping the Grout through said Exterior Grout Pipe (27) up to the top of Structure (10) and further into said respective Hollow Primary Element (11), through said Inserted Hosepipe (22), at such a slow pace (including possible planned pauses) that ensures that the height of the fresh Grout (i.e. the not yet hardened grout) within the Hollow Primary Element (11) does not exceed a predetermined value. During this process of grout filling of a single Hollow Primary Element (11), Hosepipe (22) is being retracted gradually upwards through said Inlet Opening (16), at a pace that matches the raise of the grout level within the respective Primary Element (11). Depending on the characteristics of Hosepipe (22), its retracted and exposed portion may be collected in hoops substantially at the top of Structure (10), or alternatively the exposed portion being cut off, from time to time, and the top end of the remaining Hosepipe (22) reconnected to said Grout-Feeding Subsystem; g. Following the complete filling of the first Hollow Primary Element (11) with grout, up to the prescribed final level, repeating the procedure described in points e & f above for each of the other Hollow Primary Elements (11), in a sequential order.
 2. A method according to claim 1, wherein the handling of said Inserted Hosepipe (22) is assisted by auxiliary means comprising: a. Fixing a Hand Winch (100), equipped with compatible thin Winch Rope (101) with length equal at least to substantially the initial length of Inserted Hosepipe (22), above said Inlet Opening (16) of respective Primary Element (11), with a relatively small vertical gap there between; b. Attaching said Winch Rope (101) to respective Hosepipe (22), before or during its insertion into Primary Element (11), by means of an End Fastening Device (102) located near said Hosepipe's Outlet End (105), and a plurality of Intermediate Fastenings (103) located in certain appropriate intervals throughout the inserted length of Hosepipe (22) and Winch Rope (101). The selection of specific appropriate materials and shape for Fastening Devices (102) and (103) is significantly governed by the dimensional constraints inside the cavity of said Primary Element (11), and also by the materials of Hosepipe (22) and Winch Rope (101); c. Retraction of Hosepipe (22) is facilitated by turning Hand Winch (100), while said small vertical gap between Inlet Opening (16) and Hand Winch (100) allows dismantling each Intermediate Fastening (103) as soon as it is exposed, thus allowing handling of the exposed portion of said Hosepipe (22) independently from the auxiliary means described herein.
 3. A method according to claim 1, wherein said Grout-Feeding Subsystem further comprises: (i) A grout Buffer Tank (20) of appropriate size, placed near the top of said Existing Structure (10) being reinforced, and having a bottom outlet nozzle; and (ii) A Top Grout Pump (21) (electrical or manual), placed slightly lower than said Buffer Tank (20) and connected to said Tank's outlet nozzle, directly or through a relatively short pipe there between; and wherein said top end of Exterior Grout Pipe (27), is placed right over said Buffer Tank (20) so as to feed it with fresh grout, such that Bottom Grout Pump (24) and Exterior Grout Pipe (27) are used only to “feed” Buffer Tank (20) with fresh grout at the required capacity, while Top Grout Pump (21) ensures required drive for the grout to flow along the entire length of Inserted Hosepipes (22), one of which is being connected directly to its outlet.
 4. A method according to claim 3, wherein said Grout-Feeding Subsystem does NOT include the Bottom Grout Pump (24) and the Exterior Grout Pipe (27), and instead the “feeding” of Buffer Tank (20) with fresh grout, which is being prepared utilizing said Grout Mixing Device (25) at ground level, is achieved by lifting the ready grout mix into said Buffer Tank (20) in buckets, utilizing any one of many practices exercised conventionally in the construction industry.
 5. A method according to claim 4, wherein said Grout Mixing Device (25) is located on an auxiliary platform, substantially at the top of said Existing Structure (10) being reinforced, such that it directly “feeds” Buffer Tank (20) with fresh grout, and wherein the dry grout bags may be positioned beforehand on said auxiliary platform or sufficiently close to it, so as to facilitate the mixing operation at the required pace.
 6. A method according to claim 1, wherein said filling of the cavities of said Hollow Primary Elements (11) with said Grout is done in an almost simultaneous manner (instead of sequentially), the method employing a plurality of said Inserted Hosepipes (22), such that each of said Hollow Primary Elements (11) has one of said Inserted Hosepipes (22) lowered there into, through its respective Inlet Opening (16), and the top intake end of each of said Inserted Hosepipes (22) is connected to said Grout-Feeding Subsystem only for a relatively short duration at a time, facilitating only partial filling of the respective Hollow Primary Element (11), following which the to intake end of another Inserted Hosepipe (22) is connected to said Grout-Feeding Subsystem only for a short duration, so as to facilitate similar partial filling of the other respective Hollow Primary Element (11), and this procedure is repeated with all said Inserted Hosepipes in a sequential and cyclic manner, maintaining the Grout level differences between the various Hollow Primary Elements within a predetermined value, until the grout level in all said Hollow Primary Elements (11) has reached the prescribed final levels.
 7. A method according to claim 6, wherein a Multi-Valve Distribution Block (23) is connected to the outlet of said Grout-Feeding Subsystem, the number of valves in said Distribution Block (23) being equal (or exceeding) the number of said Hollow Primary Elements (11) to be filled with Grout substantially simultaneously, and each of said top intake ends of Inserted Hosepipes (22) is connected to one respective valve in said Distribution Block (23), facilitating either simultaneous flow of the grout into all respective Hollow Primary Elements (11), or only into one of them at any given short duration, in a cyclic switching procedure, so as to achieve the same effect of almost simultaneous Grout filling at a higher comfort and speed.
 8. A method according to claim 1, wherein said filling, of said cavities, with said Gout, is monitored through a specialized Remote Portable Camera System, so as to verify that it is free of any unforeseen obstructions, the Camera (or plurality of cameras, respectively) of said System being appropriately small and durable, having an integrated flashlight; said Camera is lowered into the respective Hollow Primary Element (11) through said Inlet Opening (16) alongside with said respective Inserted Hosepipe (22), so as to provide a real-time, close-range electronic image of the filling process, and is also retracted upwards together with the respective Inserted Hosepipe (22), so as follow the rise of the grout level inside respective Primary Element (11) being filled.
 9. A method according to claim 8, wherein said Remote Portable Camera System further facilitates recording of the video signals obtained through said Camera (or plurality of cameras), thus the entire said Grout-filling process may be electronically-documented.
 10. A method for increasing the tensile load bearing capacity of all, or part of the substantially vertical Hollow Primary Elements (11) of an existing lattice frame steel structure (10), to be used in conjunction with grout-filling of said Hollow Primary Elements (11) performed by any method whatsoever, wherein said method comprises: a. Preparing a respective required quantity of a longitudinal, continuous Tensile Reinforcement Member (30), made of steel and having a Bottom End Fitting (51) designed to engage a respective Bottom Anchoring Apparatus (50), said Bottom End Fitting (51) being sufficiently small to pass through the respective top Inlet Opening (16) and through the narrowest part of the internal cavity of respective Hollow Primary Element (11); b. Preparing a respective required quantity of Top Tensioning Apparatus (60), each tailored to fit the respective typical existing top flange (15) or another existing connecting apparatus near top Inlet Opening (16) of the respective Hollow Primary Element (11), and constructed in a way that would not obstruct the insertion of the Tensile Reinforcement Member (30) into said respective Hollow Primary Element (11), and if applicable: would also facilitate the handling (namely insertion and retracting) of an Inserted Hosepipe (22); c. Inserting each of said Tensile Reinforcement Member (30) into the respective Hollow Primary Element (11), until its respective Bottom End Fitting (51) reaches the bottom of the respective Primary Element (11), and its top end is suspended from said Top Tensioning Apparatus (60); d. Installing and fixing the complete Bottom Anchoring Apparatus (50) between the bottom part of the respective Hollow Primary Element (11) and the Bottom End Fitting (51) of the respective Tensile Reinforcement Member (30); e. Applying an axial pretension of predetermined magnitude to said respective Tensile Reinforcement Member (30), through said Top Tensioning Apparatus (60); f. Filling the entire internal cavity of said respective Hollow Primary Element (11), or any part thereof as prescribed by the structural designer, with cement-based non-shrink grout.
 11. A method according to claim 10, wherein the tensioning means in said Top Tensioning Apparatus (60) comprises a conventional turnbuckle (61).
 12. A method according to claim 10, wherein the tensioning means in said Top Tensioning Apparatus (60) comprises a threaded rod (62) passing, substantially vertically, through a rigid top cover plate of Top Tensioning Apparatus (60), whereby the tensioning is applied by tightening of a top Tensioning Nut (63).
 13. A method according to claim 10, wherein said Tensile Reinforcement Member (30) is made of a plurality of long steel Rods (31) all of which having substantially equal cross-section, each of said Rods (31) having threaded end portions (34, 35) at both its ends, a plurality of Threaded Couplers (81) equipped with matching internal threads, and a Bottom End Fitting (51) equipped with matching internal thread as well, and wherein the process of installing said Tensile Reinforcement Member (30) starts with threading said Bottom End Fitting (51) onto the bottom-most of said steel Rods (31), then all said steel Rods (31) are sequentially coupled to each other, through said Threaded Couplers (81), during the process of inserting the Tensile Reinforcement Member (30) into the respective Hollow Primary Element (11).
 14. A method according to claim 10, wherein said Tensile Reinforcement Member (30) is made of a plurality of long steel Rods (31 through 33) made in several different cross-sectional dimensions, each of said Rods (31 through 33) having threaded end portions (34 through 39) at both its ends, a plurality of Threaded Couplers of several matching sizes (81, 82) equipped with matching internal threads, and a Bottom End Fitting (51) equipped with internal thread matching the bottom thread (39) of the bottom-most Rod. The number of Rods (31 through 33) may be larger than the number of different cross-sectional dimensions, such that a plurality of said rods may be of similar cross-section. Rods (31 through 33) make up a complete Tensile Reinforcement Member (30) such that its bottom portion is made of the largest cross-section Rods (33), and the cross-sections are stepping down in certain designed step-down coupling locations, wherein the top-end thread (36, 38 respectively) of the lower joining Rod (32, 33 respectively) is made smaller than the typical size thread (37, 39 respectively) of the respective Rod, so as to match the smaller size thread of the joining Coupler (81, 82 respectively), which in turn matches the thread (35, 37 respectively) of the upper joining Rod (31, 32 respectively), and wherein the process of installing said Tensile Reinforcement Member (30) starts with threading said Bottom End Fitting (51) onto the bottom-most of said steel Rods (33), then all said steel Rods (33 through 31) are sequentially coupled to each other, through said Threaded Couplers (82, 81), during the process of inserting the Tensile Reinforcement Member (30) into the respective Hollow Primary Element (11).
 15. A method according to claim 10, wherein said Tensile Reinforcement Member (30) is made of a single continuous Steel Wire Strand or Wire Rope, of uniform cross-section throughout its length, and is equipped with a Bottom End Fitting (51) engineered and mounted onto its bottom end according to any common practice known in the wire rope industry.
 16. A method according to claim 10, wherein said Tensile Reinforcement Member (30) is made of several segments of a Steel Wire Strand or Wire Rope (41 through 43), each made with a different cross-section, the bottom, thickest segment (43) is equipped with a Bottom End Fitting (51) engineered and mounted onto its bottom end according to any common practice known in the wire rope industry, and the other segments (42, 41) being coupled with each other and with the thickest segment (43) in a cross-sectional stepping down sequence, with splicing means (71, 72) based on any common practice known in the wire rope industry, so as to make up a complete Tensile Reinforcement Member (30).
 17. A method according to claim 10, wherein said Tensile Reinforcement Member (30) is made of a single continuous Steel Wire Strand, the cross-section of which consists several layers of wires arranged in concentric circles, said Tensile Reinforcement Member (30) being divided into a plurality of segments (141 through 144), the cross-sectional dimensions of said segments stepping-down respectively, said stepping-down of the Wire Strand's cross-sectional dimensions is obtained by peeling off a layer of the wires at each stepping down point, such that the cross-section of the bottom-most segment is equal to the Wire Strand's original cross-section, and the upper-most segment has the largest number of wire layers peeled off, and wherein said Tensile Reinforcement Member (30) further including a Bottom End Fitting (51) engineered and mounted onto the bottom end of its bottom segment (144) according to any common practice known in the wire strand industry.
 18. A method according to claim 17, wherein said Tensile Reinforcement Member (30) further includes protecting metal sleeves (149) of appropriate dimensions, fitted and crimped onto the Wire Strand's cross-sectional step-down points, so as to prevent undesired local deterioration of the Strand's structure at these locations during winding and handling.
 19. A method according to claim 10, wherein the longitudinal axes of all or part of the Hollow Primary Elements (11) of the existing structure have a breaking (turning) point at a certain intermediate location along their height, and said method includes the utilization of sufficient number of Restrainer (90), each being mounted onto a respective Hollow Primary Element (11) at a location close to said axial breaking point, after cutting or drilling an appropriate small opening through the wall of the respective Hollow Primary Element (11) at said location, each said Restrainer (90) being shaped and sized so as to maintain the axis of the Tensile Reinforcement Member (30) substantially concentric with that of the respective Hollow Primary Element (11).
 20. A method according to claim 19, wherein said Restrainer (90) comprises an Insert (150) inserted into the respective Hollow Primary Element (11) through a hole (160) drilled in its wall, Insert (150) being designed to stay permanently within the reinforced structure, and further comprises temporary supporting and fastening means, designed to firmly hold Insert (150) in place during the grout-filling process, all of said temporary supporting and fastening means being mounted on the exterior of the respective Hollow Primary Element (11) thus being removable and reusable; the length of insert 150 determined so as to restrain Tensile Reinforcement Member (41 in FIGS. 20, 21) in the designed, substantially concentric location, its free end shaped with an alcove matching the cross-section of Tensile Reinforcement Member (41), and its rear end equipped with a threaded bore (158) so as to facilitate connection to said temporary supporting and fastening means by a removable bolt (155).
 21. A method according to claim 20, wherein said temporary supporting and fastening means comprise a clamping device fitted to the cross-section of Hollow Primary Element (11), made commonly of 2 parts (151, 152), bolted to each other with bolts (153) and nuts (154), one respective part of the clamp (151) having a drilled hole with a location and size matching those of said threaded bore (158) in Insert (150), and a bolt (155) which secures Insert (150) onto said clamp (151).
 22. A method according to claim 10, wherein the bottom end of said existing Hollow Primary Element (11) is fitted with a flat base flange (13) leaving an opening at its bottom, wherein a certain a deliberate Vertical Gap exists between the bottom surface of Flange (13) and the concrete foundation, wherein said Bottom Anchoring Apparatus (50) is designed as a simple, monolithic Beam (180) with a height not exceeding said Vertical Gap and a length sufficiently larger than the bottom opening in Flange (13), and wherein said Bottom End Fitting (51) is shaped uniquely as a Fitting (181) equipped with a bore substantially transverse to its longitudinal axis, shaped and dimensioned to facilitate the passage of Beam (180) there through, with good dimensional fit there between.
 23. A method according to claim 10, wherein the bottom end of said existing Hollow Primary Element (11) is fitted with a flat base flange (13) leaving an opening at its bottom, wherein a certain a deliberate Vertical Gap exists between the bottom surface of Flange (13) and the concrete foundation, wherein said Bottom End Fitting (51) comprises a top part (110) mounted onto the bottom end of the respective Tensile Reinforcement Member (44 in FIGS. 10, 11 & 12), and heaving a substantially vertical threaded bore at its bottom, and a bottom part (111) which is a matching bolt, possibly having a specially shaped head, and wherein said Bottom Anchoring Apparatus (50) comprises a longitudinally & vertically split beam consisting two parts (112, 113) which may be identical or differ in shape, each containing a shaped groove, such that when the beam consisting the two parts (112, 113) is assembled, it snugly houses the head-part of bolt (111); the height of each beam part (112, 113) not exceeding said Vertical Gap, its length being sufficiently larger than the bottom opening in Flange (13), and the two beam parts (112, 113) being secured to each other after assembly with bolts (114) and nuts (115).
 24. A method according to claim 10, wherein the bottom end of said existing Hollow Primary Element (11) is fitted with a flat base flange (13) leaving a sufficiently large opening at its bottom, wherein a certain a deliberate Vertical Gap exists between the bottom surface of Flange (13) and the concrete foundation, wherein said Bottom End Fitting (51) is shaped as a Fitting (120) having two parallel flat faces on both its sides and a through-passing smooth bore with an axis substantially perpendicular to said two parallel flat faces and to the axis of the Tensile Reinforcement Member (44 in FIGS. 13, 14 & 15), and wherein said Bottom Anchoring Apparatus (50) comprises two substantially identical beams (121) clamping End Fitting (120) there between, each of said beams (121) being made of a steel plate positioned vertically, having a transverse through-passing smooth bore matching in size said bore of said End Fitting (120), and shaped such that its central portion may be somewhat higher than said Vertical Gap, said Bottom Anchoring Apparatus further comprising a relatively thick Connecting Pin (122) dimensioned to sustain the expected shear loads and long enough to secure both beams (121) onto End Fitting (120), machined smooth along its central portion and having smaller diameter threads on both ends, so as to facilitate tightening with one or two nuts (123) and large washers (124) that are larger than said smooth bores.
 25. A method according claim 24, wherein said relatively thick Connecting Pin (122) does not have said smaller diameter threads at its ends, and said clamping of said End Fitting (120) between said two plate beams (121) is secured by separate, at least two long bolts, passing transversely through both said plate beams (121) without contacting said End Fitting (120), such that tightening said separate long bolts ensures that both plate beams (121) tightly abut said two parallel flat faces on both sides of End Fitting (120), while said Connecting Pin (122) is positioned in said through-passing smooth bores of said End Fitting (120) and of both said plate beams (121).
 26. A method according to claim 10, wherein the bottom end of said existing Hollow Primary Element (11) does not include any opening (or wherein a designer's choice is not to utilize such existing opening) wherein said Bottom Anchoring Apparatus (50) is designed as a simple Beam (132), passing transversely through said existing Hollow Primary Element (11), after cutting on site two openings in its walls in appropriate sizes and locations, and optional reinforcing of the cut openings by welded plates (133, 134), in one or more layers, may be utilized such that, while the field cuttings of said Primary Element (11) might be rough and the resulting openings too large, said reinforcing plated (133, 134) may have shop-machined openings, matching the cross-sectional shape of Beam (132), thus ensuring a tight fit there between, and wherein said Bottom End Fitting (51) of the Tensile Reinforcement Member (44 in FIGS. 16, 17 & 18) is shaped uniquely as a Fitting 131 equipped with a transverse bore shaped and dimensioned to facilitate the passage of beam (132) there through, with a good geometric fit there between.
 27. A method according to claim 10, wherein said Tensile Reinforcement Member (30) is made of a combination of steel rods and wire strands or wire ropes, in various segments, spliced together so as to make up a complete Tensile Reinforcement Member (30) in the required length.
 28. A method according to claim 10, wherein the tensile load bearing capacity of the existing anchoring system, at the bottom of any Primary Element (11), is also reinforced by any procedure commonly practiced in the art, such as welding appropriate, substantially horizontal steel plates (204), having a required number of holes for additional anchoring bolts (200), onto the bottom end of said Primary Element (11), and drilling into the concrete foundation and installing with the utilization of appropriate epoxy resin (201) or the like, a required number of said additional anchor bolts (200), tightening the nuts (203) of said additional anchor bolts (200) after said resin (201) has cured, and possibly encasing the entire reinforced base in a protective mass of non-shrink concrete (202).
 29. A method according to claim 10, wherein the entire reinforcement of the structure further includes improving the load bearing capacity of secondary elements, namely certain lattice brace members of the structure, by any procedure commonly practiced in the art, such as the replacement of said certain lattice brace members of a bolted Existing Structure (10) with new brace members having larger cross-sectional area, and/or other improved properties. 